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VALVE  SETTING 


SIMPLE   METHODS   OF 

SETTING    THE    PLAIN    SLIDE   VALVE, 

MEYER    CUT-OFF,    CORLISS, 

AND   POPPET  TYPES 


COMPILED  AND  WEITTEN  BY 

HUBERT    E.   COLLINS 


FIRST  EDITION 
ELEVENTH  IMPRESSION 


McGRAW-HILL  BOOK  COMPANY,  INC, 
NEW  YORK:    370  SEVENTH  AVENUE 
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UNIVERSITY  OF  CALIFORNIA 
PAVI3 


COPYRIGHT,  1908,  BY  THE  HILL  PUBLISHING  COMPANY 


INTRODUCTION 

SUPERVISING,  operating,  and  erecting  engineers  have  long  felt  the  need 
of  a  book  giving  simple,  practical  instructions  in  the  setting  of  valves  for 
all  kinds  of  engines.  Power  has  from  time  to  time  published  articles  cov- 
ering the  leading  types,  and  this  book  is  based  on  the  material  contributed 
for  this  series. 

In  the  main,  the  articles  are  secured  from  builders  or  erecting  men  who 
are  familiar  with  the  practical  work  involved,  and  in  every  case  the  work 
has  been  passed  upon  and  approved  by  the  builders. 

Eecognizing  the  fact  that  the  fundamental  principles  of  all  valve  design 
are  contained  in  the  slide  valve  movement,  the  first  three  chapters  of  this 
book  are  given  to  a  study  of  this  subject.^  Afterwards  a  general  idea  of 
the  Meyer  valve  movement  is  given  and  then  the  Corliss. 

In  Chapter  IV,  written  by  the  compiler  of  this  book,  are  given  general 
rules  for  finding  crank  and  eccentric  centers  which  can  be  applied  to  any 
make  of  reciprocating  engine.  These  rules  are  a  valuable  aid  in  valve  set- 
ting. Careful  consideration  of  the  first  five  chapters  will  enable  a  man  to 
grasp  any  other  part  of  the  book  where  special  makes  of  engines  are  de- 
scribed, and  will  be  highly  useful  to  any  man  meeting  any  problem  in  valve 
setting,  whether  described  in  detail  in  this  book  or  not. 

The  compiler  of  this  book  is  greatly  indebted  to  the  following  men  who 
have  contributed  material  to  Power  which  is  embodied  in  this  book: 

E.  S.  Hawkins,  John  L.  Flock,  Thomas  Hall,  F.  L.  Johnson,  Carl  S. 
Dow,  F.  F.  Nickel,  Claude  Aikens,  and  E.  F.  Williams. 

HUBERT  E.  COLLINS. 
NEW  YORK,  July  1908. 


CONTENTS 


CHAPTER  PAC.K 

I.  THE  SLIDE  VALVE  EXPLAINED 3 

II.  A  STUDY  OF  THE  D  SLIDE-VALVE 19 

III.  A  STUDY  OF  THE  ZEUNER  SLIDE-VALVE  DIAGRAM 29 

IV.  THE  RIDING  CUT-OFF  VALVE 38 

V.  THE  CORLISS  STEAM  ENGINES 53 

VI.  THE  GREENE-WHEELOCK  ENGINE 62 

VII.  THE  BROWN  ENGINE 76 

VIII.  THE  MclNTosH  &  SEYMOUR  ENGINE 84 

IX.  THE  BUCKEYE  ENGINE 92 

X.  THE  PORTER-ALLEN  ENGINE 103 

XI.  THE  FITCHBURG  ENGINE Ill 

XII.  THE  FLEMING  PISTON-VALVE  ENGINES 121 

XIII.  THE  PUTNAM  ENGINE 130 

XIV.  THE  STURTEVANT  COMPOUND  ENGINE 135 

XV.  THE  RICE  &  SARGENT  ENGINE 145 

XVI.  REYNOLDS  (1890)  AND  GIRDER  FRAME  CORLISS  ENGINES       .        .        .152 

XVII.  THE  WRIGHT  STEAM  ENGINE 159 

XVIII.  THE  REYNOLDS  LONG-RANGE  CUT-OFF 172 

XIX.  THE  DUPLEX  PUMP 180 

XX.  Am  COMPRESSORS 188 

INDEX  203 


VALVE   SETTING 


THE    SLIDE    VALVE    EXPLAINED 


THE  simplest  form  of  slide  valve  is  shown  in  Fig.  1.  As  will  be  seen, 
there  is  neither  steam  lap,  positive  exhaust  lap,  nor  negative  exhaust  lap. 
The  valve  is  shown  at  the  center  of  its  travel,  that  is,  located  centrally 
over  the  ports.  The  references  S  P,  S P  denote  the  cylinder  ports;  EP 


FIG.  i. 


is  the  exhaust  port;  V  is  the  valve;  a  a  are  the  steam  edges  of  the  valve, 
and  1}  1}  the  exhaust  edges ;  c  c  are  the  exhaust  edges,  and  d  d  the  steam 
edges,  of  the  cylinder  port. 

Above  the  valve  are  shown  the  valve  circles,  one  for  each  end.  The 
eccentric  position  is  at  e  when  the  crank  is  at  c,  at  the  end  of  the  stroke. 
The  eccentric  is  90  degrees  ahead  of  the  crank  when  the  valve  has  no  lap 
nor  lead.  When  lead  is  added,  the  eccentric  will  be  advanced  to  some  posi- 
tion beyond  90  degrees,  say  to  the  point  x.  It  will  be  noted  that  if  lead 
were  added,  the  valve  and  crank  moving  in  the  direction  denoted  by  the 
arrows,  the  cylinder  port  on  the  head  end  would  be  open  to  the  admission 
of  steam  between  the  steam  edges  a  and  d  on  that  end,  and  at  the  same 
time  the  steam  would  be  exhausting  from  the  other  cylinder  port  through 

3 


4  VALVE   SETTING 

the  edges  I  and  c  on  the  crank  end.  In  Fig.  1,  there  being  no  valve  lap, 
the  travel  of  the  valve  is  equal  to  twice  the  width  of  the  port.  The  added 
lead  does  not  change  the  valve  travel,  but  causes  an  earlier  action,  as  shown 
by  the  small  diagrams  A  and  B  below  the  circles.  Of  these,  A  shows  the 
kind  of  diagram  which  would  result  with  no  lead,  while  B  shows  the  effect 
of  lead. 

LEAD  AND  LAP 

Lead,  or  the  angular  advance  of  a  valve,  is  the  amount  of  opening  to 
the  cylinder  port,  or  the  distance  between  the  edges  a  and  d  when  the 
piston  is  at  the  beginning  of  its  stroke.  (This  is  more  fully  shown  in 
Fig.  4,  where  the  arrow  A  denotes  the  direction  of  the  steam  through  such 
opening. )  The  action  of  "  lead  "  is  threefold :  First,  it  admits  steam  to 
the  piston  before  it  has  arrived  at  the  end  of  the  stroke,  and  this  steam 
acts  as  a  cushion,  enabling  the  piston  to  reverse  its  motion  easily;  second, 
it  assists  the  admission  of  steam,  tending  to  permit  the  steam  passage  to 
become  supplied  with  steam  at  full  steam-chest  pressure  by  the  time  the 
piston  reverses  its  motion;  third,  it  assists  the  exhaust,  which  is  of  espe- 
cial importance  to  a  valve  like  that  shown  in  Fig.  1. 

The  diagram  A  shows  no  early  action,  but  the  diagram  B  shows  cut-off 
before  the  end  of  the  stroke  and  release  and  compression  at  between  95 
and  100  per  cent,  of  the  stroke. 

With  no  steam  lap  nor  lead,  the  steam  is  admitted  full  stroke  and  does 
not  give  up  the  energy  which  might  be  realized  from  its  expansion.  By 
adding  lead,  one  step  in  the  right  direction  is  taken,  but  it  is  not  insufficient 
for  the  reason  that  with  a  minimum  of  lead,  with  no  steam  lap,  the  steam 
on  the  exhaust  side  cannot  escape  quickly  enough  to  prevent  its  exerting 
a  back  pressure  on  the  piston. 

"  Lap,"  as  generally  used,  and  unless  otherwise  specified,  means  steam 
lap,  and  "  steam  lap  "  means  the  amount  the  steam  edges  a  a,  Fig.  2,  over- 
lap the  steam  edges  d  d  when  the  valve  is  in  the  mid-position.  The  steam 
lap  is  provided  mainly  -to  cut  off  the  supply  of  steam  from  the  steam  chest 
into  the  cylinder  at  some  point  earlier  than  the  end  of  the  stroke,  and 
the  point  of  the  stroke  where  the  supply  is  cut  off  is  called  the  "  point  of 
cut-off."  The  determination  of  this  point  depends  upon  the  speed  of  the 
engine. 

Another  object  of  the  steam  lap  is  the  obtainment  of  free  exhaust,  which 
is  of  great  importance  in  a  high-speed  engine.  Increased  valve  lap  calls 
for  increased  travel,  which  also  aids  exhaust. 

The  difference  in  valve  travel,  with  and  without  lap,  will  be  seen  by 
comparison  of  the  valve-travel  circles  in  Figs.  1  and  2.  In  Fig.  1  it 
is  shown  that  the  valve  travel  equals  twice  the  width  of  the  port,  while 


THE   SLIDE   VALVE   EXPLAINED  5 

Fig.  2  shows  that  the  valve  travel  is  equivalent  to  twice  the  width  of 
the  port  plus  the  lap.  When  the  valve  is  in  mid-position,  as  in  Fig.  2, 
the  steam  edges  a  a  are  in  positions  corresponding  to  the  center  of  travel 
a' a'.  At  this  point  the  valve  is  lapped  on  the  steam  edges,  and  the  ex- 
haust edges  b  I,  not  being  lapped,  are  line  and  line  with  the  exhaust  edges 
c  c  of  the  cylinder  ports.  When  the  valve  moves  in  one  direction,  so  that 
one  steam  edge  a  of  the  valve  becomes  even  with  the  steam  edge  d  of 
the  port,  it  will  correspond  with  the  point  df  in  the  valve  circle;  while 
the  other  edge  a  has  advanced  to  the  point  /  on  the  valve  seat,  which  cor- 
responds to  the  point  /'  in  the  valve  circle,  and  the  edge  b  on  this  end 


FIG.  2. 


has  advanced  to  the  edge  d  of  the  steam  port.  The  valve  would  then  be 
in  position  to  admit  steam  to  one  port  and  leave  the  opposite  port  wide 
open  for  exhaust. 

Where  the  edge  a  of  the  valve  has  advanced  to  the  edge  c  of  the  cyl- 
inder port,  the  opposite  edge  a  has  advanced  to  the  point  e  on  the  valve 
seat,  corresponding  to  the  point  e'  in  the  valve  circle.  The  steam  port 
OIL  the  one  side  is  now  wide  open,  and  the  exhaust  port  on  the  other  side 
is  still  wide  open.  At  this  juncture  the  valve  has  reached  the  limit  of  its 
travel  in  one  direction,  and  upon  reversing  its  travel  the  first  edge  a  of 
the  valve  reaches  the  edge  d  of  the  port  and  cuts  off  the  steam  at  about 
three  quarters  of  the  piston  travel.  The  valve  continuing  until  the  edge 
a  meets  the  point  a  on  the  valve  seat,  the  exhaust  has  again  closed  on  one 
end  and  is  about  to  open  at  the  other  end;  and  so  the  action  continues. 


G 


VALVE   SETTING 


TRACING  THE  ACTION  IN  DETAIL 

To  get  a  more  complete  understanding  of  this,  it  will  be  well  to  follow 
the  valve  action,  by  means  of  Fig.  3  and  succeeding  illustrations,  through 
one  complete  revolution  of  the  crank  of  the  engine.  The  lap  represented 
is  25  per  cent,  of  the  travel,  the  two  valve  circles  being  so  placed  with 
reference  to  the  valve  as  to  clearly  indicate  the  action  of  each  end.  In 
all  the  illustrations  the  position  of  the  crank  on  the  circle  is  shown  at  c, 


FIG.   3. 


and  the  position  of  the  eccentric,  in  relation  to  the  crank,  at  e.  The 
graduated  scale  in  several  of  the  crank-end  circles  is  for  convenience  in 
identifying  the  position  of  the  crank  in  per  cent,  of  stroke  at  any  point 
of  the  valve  movement.  The  point  of  intersection  with  the  line  B  B  of 
the  arc  of  a  circle  which  would  bisect  the  crank-end  circle  C  shows  the 
relative  position  of  the  piston  in  per  cent,  of  its  stroke.  The  valve  circles 
are  marked  II  and  C  to  indicate  the  head  and  crank  ends  of  the  cylinder, 
respectively.  The  arrows  denote  the  direction  of  movement,  and  the  ports 
and  edges  are  the  same  as  in  Figs.  1  and  2. 


THE   SLIDE   VALVE   EXPLAINED  7 

Fig.  3  shows  the  valve  about  to  open,  with  the  position  of  the  eccentric 
e,  in  relation  to  the  position  of  the  crank  c,  as  shown,,  or  when  the  angle 
of  advance  is  just  sufficient  to  overcome  the  lap.  With  the  angular  ad- 
vance no  greater  than  that  indicated,  diagrams  such  as  those  shown  beneath 
the  circles  are  obtained,  the  principal  features  of  which  are  cut-off  when 
near  75  per  cent,  of  the  piston  travel  and  release  and  compression  at  from 
90  to  95  per  cent,  of  the  stroke.  It  will  be  noted  that  while  the  exhaust 
(owing  to  greater  valve  travel  than  shown  in  Fig.  1)  is  full  open  at  the 
same  position  of  the  crank,  neither  release  nor  compression  sets  in  much 
earlier  in  the  stroke. 

In  Fig.  4  the  same  valve  is  given  lead,  while  the  crank  still  remains 
at  the  beginning  of  the  stroke.  This  admits  steam  in  the  direction  of 


L 


FIG.    4. 


the  arrow  A,  the  exhaust  being  in  the  direction  of  the  arrow  B  at  the 
same  time. 

In  Fig.  5  the  head-end  steam  port  is  full  open  at  the  same  time  that 
the  crank-end  exhaust  is  still  full  open.  The  eccentric  e  is  at  the  end 
of  its  travel  and  the  crank  c  is  relatively  in  the  position  shown.  The 
piston  would  be  at  about  30  per  cent,  of  its  travel. 


8 


VALVE   SETTING 


Fig.  6  shows  the  valve  at  the  point  of  cut-off  for  the  head  end.  The 
steam  is  cut  off  and  the  exhaust  still  remains  open  on  the  crank  end. 
The  piston  has  reached  about  75  per  cent,  of  its  travel,  with  the  crank 
and  eccentric  as  shown. 

Fig.  7  shows  the  exhaust  about  to  release  on  the  head  end,  and  just 
closed  for  compression  on  the  crank  end.  The  piston  has  reached  nearly 
93  per  cent,  of  stroke. 

Fig.  8  shows  the  cylinder  port  on  the  head  end  wide  open  for  exhaust, 
and  the  crank  end  of  the  valve  open  for  lead  on  the  crank-end  port,  with 
the  piston  at  the  beginning  of  its  return  stroke. 


FIG.   5. 


Fig.  9  shows  the  valve  having  reached  the  extreme  of  its  travel  in 
the  direction  shown,  leaving  the  head-end  port  wide  open  for  exhaust  and 
the  crank-end  port  wide  open  for  steam,  the  piston  having  advanced  to 
about  25  per  cent,  of  its  return  stroke. 

Fig.  10  shows  the  valve  at  the  point  of  cut-off  on  the  crank  end,  with 
the  head-end  port  still  open  to  the  exhaust.  The  piston  in  this  case  will 
not  have  traveled  quite  as  far  as  it  did  on  the  head-end  cut-off. 

Fig.  11  shows  the  valve  centered  on  its  travel  again,  with  the  exhaust 


THE   SLIDE   VALVE   EXPLAINED 


9 


just  closed  on  the  head  end,  and  at  the  point  of  release  on  the  crank  end. 
The  piston  has  reached  about  90  per  cent,  of  its  return  travel. 


How  THE  INDICATOR  DIAGRAM  is  MADE 

Suppose  an  indicator  were  located  at  each  end  of  the  cylinder,  with 
the  pencil  points  in  contact  at  the  beginning  of  the  valve  action  shown  in 
these  illustrations,  for  the  purpose  of  making  simultaneous  records.  Then 
referring  back  to  Fig.  4,  it  will  be  found  that  the  line  of  admission  has 
been  recorded  on  the  head  end  and  the  line  of  release  on  the  crank  end. 


FIG.   6. 


Fig.  5  shows  the  admission  line  being  recorded  on  the  head  end  and  the 
counter-pressure  line  on  the  crank  end.  Fig.  6  shows  the  admission  line 
on  the  head  end  completed  up  to  the  point  of  cut-off,  and  the  counter- 
pressure  line  on  the  crank  end  still  extending.  Fig.  7  shows  that  the 
expansion  line  on  the  head  end  has  been  developed  to  the  point  of  release, 
and  the  counter-pressure  line  on  the  crank  end  has  arrived  at  the  point 
of  compression,  or  exhaust  closure.  Fig.  8  shows  that  the  release  line  on 
the  head  end  has  developed,  and  that  compression  and  admission  have 


10 


VALVE   SETTING 


occurred  on  the  crank  end.  Fig.  9  shows  the  start  of  the  counter-pressure 
line  on  the  head  end,  and  the  admission  line  on  the  crank  end,  also.  Fig. 
10  shows  the  head-end  counter-pressure  line  still  extending  and  the  crank- 
end  admission  line  extended  to  the  point  of  cut-off.  Fig.  11  shows  the 
completed  action  with  the  following  approximate  results: 


Head  End 

Crank 
End 

Cut-off  per  cent  of  stroke            

75 

73 

Release  per  cent  of  stroke       

91 

90 

Compression  per  cent,  of  stroke  

90 

91 

POSITIVE  AND  NEGATIVE  EXHAUST  LAP 

In  adding  sufficient  steam  lap  to  bring  about  good  cut-off,  the  exhaust 
is  apt  to  be  released  too  early,  and  exhaust  lap  is  provided  to  obviate  such 


M 


FIG.    7. 


defect.  Exhaust  lap  is  the  amount  the  exhaust  edges  (I  I,  Fig.  12)  of 
the  valve  overlap  the  exhaust  edges  c  c  of  the  cylinder  ports  when  the 
valvs  is  in  mid-position,  as  shown.  In  Fig.  12  the  valve  travel  is  equal 


THE   SLIDE   VALVE   EXPLAINED 


II 


to  twice  the  width  of  the  port  plus  the  steam  and  exhaust  lap,  with  the 
center  and  extremes  of  travel  as  shown  by  the  circle. 

Where  valves  require  small  steam  lap  or  excessive  travel,  it  is  sometimes 
necessary  to  provide  negative  or  exhaust  clearance  to  free  the  exhaust. 
Negative  lap  or  exhaust  clearance  is  the  amount  of  opening  (Fig.  13) 
between  the  exhaust  edges  bb  of  the  valve  and  the  exhaust  edges  c  c  of 
the  cylinder  ports  when  the  valve  is  in  the  mid-position  of  its  travel.  In 


FIG.   8. 


Fig.  13  the  valve  travel  will  equal  twice  the  width  of  the  port,  plus  the 
steam  lap,  as  in  Fig.  2. 


OTHER  IMPORTANT  CONSIDERATIONS 

Eeferring  to  Fig.  14,  linear  advance  of  an  eccentric  is  the  linear  dis- 
tance equaling  the  lap  and  lead  measured  on  a  like  perpendicular  to  the 
90-degree  radius  H  c,  meeting  the  circumference  of  the  circle  of  the  eccen- 
tric revolution,  as  at  B.  The  distance  A  B  is  the  linear  advance. 

Angular  advance  of  an  eccentric  is  the  angle  corresponding  to  a  sine 
whose  length  is  twice  the  lap  in  per  cent,  of  travel.  For  example,  the 
angle  H  c  B,  Fig.  14. 


12 


VALVE  SETTING 


EXAMPLE 

The  steam  lap  is  assumed  to  be  25  per  cent,  of  the  valve  travel  and 
there  is  no  lead;  what  is  the  angular  advance? 

The  valve  travel  in  the  illustration  (Fig.  14)  is  proportional  to  the 
line  E  F.  Twenty-five  per  cent,  of  this  multiplied  by  two  equals  one  hall 
of  the  radius  cF.  By  referring  to  a  table  of  natural  sines,  it  is  seen 
that  the  angle  corresponding  to  a  sine  equaling  0.50  is  30  degrees.  In 
this  case,  then,  30  degrees  is  the  angular  advance. 


FIG.   9. 


In  case  there  is  lead,  the  lead  angle  must  be  added,  as  follows:  Lap, 
26  per  cent.;  lead,  2  per  cent.;  total,  27  per  cent.  Then,  27  X  2  =  0.54. 
Referring  again  to  the  table,  the  angle  of  advance  is  found  to  be  32  degrees 
minus  41  minutes. 

The  angle  of  admission  is  the  angle  the  crank  pin  passes  through  (be- 
ginning at  the  end  of  the  stroke)  prior  to  cut-off.  It  is  always  180  de- 
grees minus  twice  the  angular  advance,  as,  for  example,  the  angle  E  cB, 
Fig.  14.  In  .the  above  example,  the  angle  of  admission  would  be  180 


THE   SLIDE   VALVE   EXPLAINED 


13 


degrees  —  (32  degrees  41  minutes  X  2)  —  114  degrees  38  minutes.  It  fol- 
lows that  if  there  were  no  lap,  there  would  be  no  angular  advance,  as 
shown  in  the  valve  circle  in  Fig.  1,  and  the  angle  of  admission  would  be 
180  degrees,  or  full  stroke.  On  the  other  hand,  if  the  lap  equaled  50 
per  cent,  of  the  valve  travel,  the  sine  of  the  angular  advance  becomes  1, 
and  the  angular  advance  is  90  degrees,  which  multiplied  by  two  equals 
180  degrees,  and  there  would  be  no  angle  of  admission,  as  180  — 180  =  0 ; 
and  steam  would  be  cut  off  at  the  beginning  of  stroke,  there  being  no 
lead.  If  lead  were  used,  the  angle  of  admission  would  be  that  due  to  the 


FIG.  10. 


lead  only.     The  above  examples  serve  when  the  admission  is  greater  than 
50  per  cent,  of  the  stroke. 

The  period  of  admission,  when  less  than  50  per  cent,  of  the  stroke,  is 
equal  to  one  half  the  versed  sine  of  the  angle  of  admission,  as  A  B,  Fig. 
15.  If  the  cut-off  occurs  beyond  the  half  stroke,  the  period  of  admission 
equals  one  half  the  stroke  plus  one  half  the  sine  of  the  angle  exceeding 
90  degrees,  as  TICK,  Fig.  16. 


14 


VALVE   SETTING 


EXAMPLE 

The  lap  equals  40  per  cent,  of  the  valve  travel.  This  equals  40  X  2  = 
0.80  radius.  The  angular  advance  therefore  is  the  angle  corresponding  to 
a  sine  0.80.  The  angle  is  53  degrees  15  minutes;  the  angle  of  admission, 
therefore,  is  180  degrees —  (53  degrees  15  minutes  X  2)  =  73  degrees  30 
minutes,  which  is  less  than  one-quarter  revolution  or  one-half  stroke.  The 
period  of  admission  is  actually  one  half  the  versed  sine  of  73  degrees  30 


FIG  11. 


minutes,  which  is  equal  to  47.9  per  cent,  of  stroke.  Eefer  again  to  Fig. 
15,  in  which  K  C  A  is  the  angle  of  admission,  either  angle  LCD,  K  C  L, 
or  A  C  P  being  the  angular  advance,  and  RP  the  linear  advance  equaling 
the  lap. 

If  the  lap  were  30  per  cent,  of  the  valve  travel,  the  angular  advance 
would  be  30  X  2  =  0.60  =  37  degrees,  and  the  angle  of  admission  would 
be  180 —  (37  X  2)  =  106  degrees,  and  the  period  of  ad  minion  would  l><; 
one  half  the  versed  sine  of  90  degrees  plus  one  half  the  sine  of  16  degrees, 
or  63  per  cent,  of  the  stroke. 


THE  SLIDE  VALVE  EXPLAINED 


15 


THE  EXHAUST 

Assuming  no  exhaust  lap,  the  opening  and  closing  will  occur  when  a 
portion  of  the  stroke  equaling  one  half  the  versed  sine  of  the  angular 
advance  is  still  incompleted.  That  is  to  say,  the  angle  of  compression  and 
the  angle  of  prelease  are  equal  to  each  other  and  equal  also  to  the  angle 
of  advance.  It  follows  that  if  the  lap  is  50  per  cent,  of  valve  travel,  the 
angular  advance  would  be  90  degrees,  with  the  exhaust  opening  and  closing 
at  50  per  cent,  of  the  stroke.  On  the  other  hand,  if  there  were  no  steam 
lap  nor  lead,  there  would  be  no  angular  advance,  and  the  exhaust  would 
open  and  close  at  the  end  of  the  stroke. 


ANGULARITY  OF  THE  CONNECTING  ROD 

The  angularity  of  the  connecting  rod  with  the  center  line  lengthens 
the  admission  on  the  head  end  and  shortens  it  on  the  crank  end,  as  has 


FIG.  12. 


been  shown  in  Figs.  4  to  11,  inclusive,  and  summed  up  at  the  end  and 
further  explained  here.  The  amount  the  cut-off  is  retarded  during  the 
out  stroke  and  hastened  during  the  in  stroke  depends  upon  the  ratio  of  the 
length  of  the  rod  to  the  crank  travel.  In  the  examples  already  given, 
the  ratio  of  rod  to  travel  was  3  to  1.  The  point  of  cut-off  also  depends  on 
the  position  of  the  crank  at  the  time  cut-off  occurs.  The  amount 
the  admission  is  lengthened  on  the  out  stroke  (or  the  down  stroke  of  a 


16 


VALVE   SETTING 


vertical  engine),  and  shortened  on  the  in  stroke  (or  the  up  stroke  of 
a  vertical  engine),  by  the  angularity  of  the  connecting  rod,  is  the  versed 
sine  of  the  aiiyle  of  Hie  rod  multiplied  by  the  ratio  of  the  crank  ifiridcd 
by  two. 

The  angle  of  the  rod  may  be  found  by  dividing  the  sine  of  the  crank 


FIG.  13. 


angle  by  the  ratio  of  the  rod  to  the  crank.     The  quotient  is  the  sine  of 
the  angle  of  the  rod. 

EXAMPLE 

Assume  the  crank  angle  to  be  60  degrees.  The  sine  of  60  degrees  = 
0.866.  This  sine  divided  by  the  ratio  of  the  rod  to  the  crank  (say  6)  = 
0.144,  which  is  the  sine  of  the  connecting  rod,  and  the  angle  is  8  degrees, 
nearly.  Again,  the  reversed  sine  of  8  degrees  =  0.00973.  This  multiplied 
by  6  -f-  2  =  2  per  cent.,  nearly,  which  is  the  amount  the  admission  is  length- 
ened on  the  out  stroke  and  shortened 
on  the  in  stroke.  The  exhaust  is  af- 
fected in  the  same  way,  only  as  the 
crank  angles  are  smaller  at  exhaust, 
the  full  effect  is  not  so  great,  as  is 
shown  by  table  of  results  of  valve 
movements.  The  nearer  to  the  one- 
half  stroke  of  the  crank  the  cut-off  or 
release  and  compression  occur,  the 
greater  the  amount  of  difference  in  per 
cent,  on  the  two  strokes,  and  the 
nearer  the  beginning  and  end  of  the 
stroke  the  less  the  percentage. 

It   has  been  shown  that  the  pre- 
exhaust  angle  equals  the  angular  ad- 
vance (when  no  inside  lap  is  used).     Therefore,  the  sine  of  the  angle  of 
the  connecting  rod  at  exhaust  is  the  sine  of  that  angular  advance  of  the 
eccentric  which  equals  the  lap  and  lead. 


THE   SLIDE   VALVE   EXPLAINED 


17 


EXAMPLE 

Assume  the  lap  to  be  30  per  cent,  of  the  valve  travel  or  0.60  radius. 
The  lap  being  the  sine  of  the  angular  advance,  it  will  be  6  times  the  sine 
of  the  connnecting-rod  angle,  0.60  -f-  6  =  0.10.  which  is  the  sine  of  the 
latter,  and  the  angle  is  5  degrees  45  minutes. 

The  reversed  sine  of  5  degrees  45  minutes  is  0.005.  The  point  of  ex- 
haust, therefore,  would  be  delayed  0.005  X  (6  f-  2)  =  0.015  per  cent,  of 


N 


FIG.    15. 


the  out  or  down  stroke,  and  hastened  the  same  per  cent,  on  the  in  or  up 
stroke. 

To  correct  for  the  angularity  of  the  rod,  it  is  customary  to  give  less 
lead  at  the  head  end  than  at  the  crank  end.  It  may  be  done  also  in  the 
arrangement  of  the  valve  gear  where  rockers  are  used,  placing  the  rocker 
arms  in  such  position  as  to  give  the  valve  more  rapid  opening  and  closing 
movements  on  the  head  end  than  on  the  crank  end.  Professor  Sweet  pro- 
vides for  equal  cut-off  in  this  manner.  Similar  construction  has  been  used 
by  Mr.  Williams  and  other  designers. 

Providing  greater  lead  at  the  crank  end  than  at  the  head  end  not  only 
serves  to  correct  the  admission  but  the  exhaust  also,  only  it  is  not  sufficient 


FIG.    16. 


for  the  latter.  To  equalize  the  compression,  therefore,  it  is  customary  to 
use  less  inside  exhaust  lap  at  the  head  end  than  at  the  crank  end.  Or,  the 
crank  end  may  be  made  line  and  line  if  the  cylinder  clearance  is  small, 
and  the  lap  at  the  head  end  is  cut  away  so  as  to  give  negative  lap  at  that  end 


18  VALVE  SETTING 

when  the  valve  is  centrally  located.  About  from  1  to  3  per  cent,  is  gen- 
erally sufficient,  the  object  being  to  reduce  the  terminal  compression  at 
both  ends  to  about  three  fourths  of  initial  compression. 

When  the  rods  are  very  short,  as  in  marine  engines  (sometimes  of  as 
low  as  1.7  ratio),  it  is  quite,  or  almost,  impossible  to  equalize  the  cut-off 
with  a  single  valve,  and  also  very  little  loss  occurs  from  a  moderate  degree 
of  inequality. 

METHOD  OF  LAYING  OUT  VALVE  MOTION 

In  Figs.  15  and  16  is  shown  a  method  of  laying  out  the  valve  motion 
used  by  E.  F.  Williams,  designing  engineer,  which  recommends  itself  on 
account  of  its  simplicity.  The  lines  MD  are  drawn  to  represent  the 
center  line  of  the  engine  indefinite.  From  C  as  a  center,  draw  the  circum- 
ference P  A  K II L  D,  representing  both  the  travel  of  the  crank  pin  and 
that  of  the  eccentric.  Draw  the  vertical  downward  from  the  center  line 
a  distance  equaling  the  lap  and  lead,  meeting  the  travel  circle  at  P.  Draw 
the  diameter  P  L  and  erect  the  perpendicular  L  F.  The  distance  A  F  is 
the  travel  of  piston  prior  to  release,  and  the  distance  F  D  is  the  pre-release. 
Make  the  angle  K  C  D  equal  to  twice  the  angular  advance  LCD',  the 
remaining  angle  K  C  A  (shaded)  is  the  angle  of  admission,  and  the  period 
of  admission  is  A  B,  the  connecting  rod  being  considered  infinite. 

To  correct  for  the  angle  of  the  rod,  draw  the  line  M  K  for  the  steam 
admission,  and  the  line  N  L  for  the  exhaust,  making  the  ratio  of  M  K 
to  K  C  and  N  L  to  L  C  equal  to  the  ratio  of  the  connecting  rod  to  the 
crank.  From  the  points  M  and  N  scribe  the  arcs  K  E  and  L  0. 

The  point  E  will  be  the  point  of  cut-off  and  G  the  point  of  release, 
corrected  for  the  angles  of  the  connecting  rod. 


II 


A    STUDY    OP    THE    D    SLIDE   VALVE* 


IT  will  now  be  in  order  to  take  up  more  in  detail  the  effects  of  chang- 
ing the  valve  setting,  and  the  methods  of  using  the  diagram  for  de- 
signing and  proportioning  valves  for  new  engines  or  for  remodeling 
valves  in  engines  already  in  operation.  It  will  be  seen  in  Fig.  17  that 
if  the  outside  lap  is  increased  an  amount  corresponding  to  N — M  on  the 
scale  of  the  diagram,  admission  will  take  place  later,  at  the  crank  posi- 
tion 0 — A',  where  the  lead  will  be  reduced  to  I — G9  and  cut-off  will  take 
place  earlier  at  0 — C".  On  the  other  hand,  the  contrary  effects  are  seen 
where  the  outside  lap  is  reduced,  and  if  the  inside  lap  be  increased  an 
amount  equal  to  L — 8  release  willtake  place  later,  or  at  the  crank  posi- 


FIG.    17. 


FIG.    18 


tion  0 — Bf,  and  compression  will  take  place  earlier,  at  0 — D',  the  effect 
being  exactly  opposite  for  a  decrease  of  the  inside  lap. 

In  Fig.  18  is  shown  the  effect  of  altering  the  angular  advance  of  the 
eccentric.  It  will  be  seen  that  if  the  angle  of  advance  is  increased,  as 
at  a',  all  the  events  of  the  valve  occur  earlier,  since  the  crank  revolves 
in  the  direction  indicated  by  the  arrow,  and  the  new  position  of  admission 
0 — A!  is  ahead  of  0 — /4,  the  old  position.  This  is  true  also  of  the  other 
valve  movements,  0 — Ef  being  ahead  of  0 — E,  and  0 — C"  ahead  of  0 — C. 


*  Contributed  to  POWER  by  E.  S.  Hawkins. 
19 


20 


VALVE   SETTING 


A  third  alteration  that  may  be  made  in  the  valve  gear  is  a  change  of 
eccentricity,  by  altering  the  eccentric  radius,  when  making  a  design,  or 
by  using  a  new  eccentric  of  radius  different  from  that  of  the  older  one, 
where  an  engine  is  being  rebuilt.  The  effect  of  a  change  in  eccentricity 
is  shown  in  Fig.  19,  in  which  it  will  be  noted  that  when  the  eccentricity 
is  increased,  the  valve  travel  is  increased,  and  admission  takes  place  ear- 
lier (at  0 — A)9  the  lead  being  in- 
creased an  amount  equal  to  / — I', 

/y/^x^^xNT^vy  \  while   cut-off   takes    place   later    (at 

fwC\      \\/\ABB    °~  c');  °~ R  in  the  figure  comes 
/    Y  V         A — r  •^S&*\\       aneacl  of  ^ — B>  showing  that  release 

is  earlier  the  greater  the  eccentricity 
and,  since  0 — D'  comes  after  0 — D, 
it  is  plain  that  compression  is  later. 
Since  the  upper  valve  circle  cuts  the 
arc  drawn  from  0  as  the  center,  with 
a  radius  equal  to  the  outside  lap  plus 
the  width  of  the  steam  port,  in  the 
points  W  and  H',  the  admission  port 

will  be  open  wide,  while  the  crank  moves  from  0 — W  to  0 — H'.  On  the 
lower  valve  circle  it  is  shown  tha£  the  exhaust  port  opens  sooner  (at  IF) 
and  remains  open  longer  (at  H).  It  is  plain,  of  course,  that  decrease  of 
the  eccentricity  will  have  a  contrary  effect. 

TABLE  SHOWING  IN  CONDENSED  FORM  EFFECT  OF  CHANGES  IN  LAP,  TRAVEL  OF  VALVE, 
OR  ANGULAR  ADVANCE  OF  ECCENTRIC 


FIG.   19. 


Increasing 
Outside  Lap 

Increasing 
Inside  Lap 

Increasing 
Travel 

Increasing 
Angular 
Advance 

Admission  

1 

Is  later 
Ceases  sooner 

Not  changed 

Begins  earlier 
Continues  longer 

Begins  earlier 
Same  period 

Expansion  

1 

Is  earlier 
Continues  longer 

Beginning 
unchanged 
Continues  longer 

Begins  later 
Ceases  sooner 

Begins  earlier 
Same  period 

Exhaust  

I 

Unchanged 

Occurs  later 
Ceases  sooner 

Begins  earlier 
Ceases  later 

Begins  earlier 
Same  period 

Compression.  .  .  . 

i 

Begins  at 
same  point 

Begins  sooner 
Continues  longer 

Begins  later 
Ceases  sooner 

Begins  earlier 
Same  period 

The  accompanying  table  shows  in  condensed  form  the  effect  of  changes 
in  the  lap,  travel  of  the  valve,  or  the  angular  advance  of  tne  eccentrit 


A  STUDY  OF  THE   D   SLIDE   VALVE  21 

From  what  has  been  said,  it  will  be  seen  that  in  all  problems  using 
the  valve  diagram.,  there  are,,  in  addition  to  the  four  valve  movements  of 
admission,  cut-off,  release,  and  compression,  the  other  variables  of  valve 
travel,  angle  of  lead,  outside  lap,  and  inside  lap.  In  every  problem,  some 
of  these  items  are  given  and  the  others  must  be  found  and,  in  designing 
an  engine,  the  conditions  under  which  it  is  to  be  used  determine  certain 
of  the  elements  which  are  then  considered  fixed,  and  are  used  in  com- 
putations to  determine  the  other  variables.  In  general,  the  work  of  any 
case  will  fall  under  one  of  five  problems,  each  of  which  will  be  here 
explained. 

PROBLEM  I.  Given  the  travel  of  valve  and  points  of  admission, 
cut-off,  and  release. 

In  Fig.  20,  let  C — P3  equal  the  given  travel  of  the  valve,  and  on  this 
line  as  a  diameter  construct  a  circle,  marking  on  it  the  points  K,  P,  and  P2 
for  the  given  points  of  admission,  cut-off,  and  release.  Through  K  and  P 
draw  the  line  K — P,  and  through  0  draw  the  line  C3 — C4  perpendicular 
to  the  line  K— P.  From  P2  draw  the  line  P2—K1  parallel  to  K— P, 
and  intersecting  the  line  C3 — C4  at  the  point  M19  the  distance  of  which 
from  the  center  0  is  the  exhaust  lap  of  the  valve,  while  the  similar  dis- 
tance of  the  point  M  on  the  line  K — P  from  the  center  0  is  the  lap  of  the 
steam  valve.  By  drawing  in  the  valve  circles  and  the  lap  circles  through 
the  points  M  and  M1}  the  leads  N — Q  and  N^ — Q±  are  determined. 

PROBLEM  II.  Given  the  travel  of  valve,  steam  lap,  steam  lead,  and 
any  point  in  the  exhaust  diagram. 

In  this  case  the  crank  circle  is  constructed  as  before,  and  the  distance 
0 — N  laid  off  equal  to  the  lap  plus  the  lead.  At  the  point  N  the  per- 
pendicular N — Cs  is  erected,  cutting  the  crank  circle  in  the  point  (73. 
It  is  plain  then  that  the  angle  (73 — 0 — R  is  the  angle  of  advance  and 
the  diagram  is  completed  by  drawing  the  diameter  Ca — 0 — (74,  and  fol- 
lowing out  the  construction  by  drawing  in  the  valve  and  lap  circles. 

PROBLEM  III.     Given  the  travel  of  valve,  cut-off,  steam  lead,  and  ex- 
haust lap. 

First  construct  the  valve  circle  as  before  and  mark  on  it  the  point 
P  corresponding  to  the  point  of  cut-off.  With  the  point  C  as  a  center 
and  a  radius  equal  to  the  lead  (which  is  given),  draw  in  a  circle,  as 
shown  in  the  figure,  and  from  the  point  P  draw  a  line  passing  tangent 
to  this  circle  on  the  under  side.  This  line  will  cut  the  large  circle  at 
the  point  K,  which  is  the  point  of  admission.  By  drawing  a  diameter 
through  the  point  0  perpendicular  to  the  line  K — P  the  angle  of  advance 
is  determined,  after  which  the  rest  of  the  construction  can  readily  be 
carried  out. 

PROBLEM  IV.  Given  the  steam  lap,  steam  lead,  and  the  point  of 
cut-off. 


22 


VALVE   SETTING 


In  Fig.  20,  let  the  angle  C — 0 — P  be  that  corresponding  to  the  point 
of  cut-off  and  draw  in  the  lap  circle  Q  M  L,  laying  off  at  the  same  time 
the  distance  Q — N  equal  to  the  lead.  Connect  the  points  N  and  0  and 
the  points  0  and  L  by  straight  lines,  and  erect  a  perpendicular  to  each 
of  these  lines  at  its  middle  point.  The  point  0±  at  which  these  two 
perpendiculars  intersect  will  be  the  center  of  the  steam-valve  circle  and 
the  radius  will  be  the  distance  from  it  to  the  point  0,  or  either  of  the 
points  N  and  L.  The  diameter  of  this  circle  is,  of  course,  equal  to  one 
half  the  travel  of  the  valve,  so  that  the  crank  circle  may  readily  be 
constructed,  and  the  angle  Cs — 0 — R  between  the  diameter  of  the  valve 
circle  and  the  perpendicular  erected  from  the  point  0  will  be  the  angle 
of  advance.  It  is,  then,  an  easy  matter  to  carry  out  the  construction  and 


c. 


FIG.    20. 


FIG.    21. 


finish  the  diagram  by  drawing  in  the  other  valve  circle  and  the  two  lap 
circles,  and  laying  off  on  the  crank  circle  the  points  corresponding  to  the 
other  valve  movements. 

PROBLEM  V.  Given  the  cut-off,  release,  compression,  and  width  of 
port. 

It  is  assumed  that  the  width  of  the  port  is  equal  to  the  maximum 
opening  of  the  exhaust  port,  and  to  construct  the  diagram  it  will  first 
be  necessary  to  find  the  travel  of  the  valve,  which  is  done,  as  shown  in 
Fig.  21,  by  drawing  a  circle  of  indefinite  radius  and  marking  on  it  points 
of  cut-off,  release,  and  compression.  This  can  readily  be  done,  since  these 
points,  if  given  in  terms  of  the  stroke,  as  explained  in  Chapter  III, 
may  be  found  in  terms  of  the  angle  turned  through  by  the  crank.  Join 
the  points  of  release  and  compression  by  the  line  A — B  and  through  0 
draw  a  diameter  perpendicular  to  this  line.  It  is  then  plain  that  the 
ratio  of  valve  travel  to  the  given  width  of  port  is  equal  to  the  ratio  of 
W — Y  to  X — F;  and  from  this  the  travel  of  the  valve  is  obtained  and 
used  as  the  diameter  of  a  new  crank  circle,  which,  when  drawn,  has  the 


A   STUDY  OF  THE   D  SLIDE   VALVE  23 

points  of  cut-off,  release,  and  compression  laid  down  and  the  diagram 
drawn  as  per  the  problem  already  given. 

Sometimes  the  point  of  release  is  given  instead  of  the  width  of  port, 
and  in  this  case  the  travel  of  valve  is  found  by  drawing  through  the 
point  P  a  line  parallel  to  A — B  and  from  the  point  C  dropping  a  per- 
pendicular to  this  line  at  E.  The  line  C — E  is  then  proportional  to  the 
lead,  so  that  we  have  the  ratio  travel  of  valve  to  given  lead  equals  W — Y 
to  C — E,  from  which  the  travel  of  valve  is  found  as  before.  In  these 
cases  the  distance  W — Y  is  multiplied  by  the  width  of  port  or  by  the 
given  lead,  as  the  case  may  be,  and  the  product  divided  by  the  distance 
X — Y  or  C — E,  to  find  the  travel  of  the  valve  in  actual  inches.  This 
dimension  must,  of  course,  be  altered  to  correspond  with  the  scale  selected 
for  drawing  the  diagram. 

As  illustrations  of  the  practical  working  of  the  diagram  a  number  of 
examples  with  solutions  will  be  given. 

1.  Travel  of  the  valve  is  6  ins.  and  cut-off  occurs  when  the  crank  has 
completed  105  degrees  of  its  path.  Admission  of  steam  begins  when  the 
crank  is  within  7.5  degrees  of  the  beginning  of  its  stroke,  and  exhaust 
closes  when  it  is  60  degrees  from  the  end  of  its  stroke.  Construct  the 
Zeuner's  valve  diagram  and  find  the  steam  lap,  steam  lead,  exhaust  lap, 
exhaust  lead,  and  the  angle  of  advance. 

As  the  first  step,  select  some  scale  to  which  the  diagram  is  to  be  drawn 
and,  as  in  this  case  the  travel  is  6  ins.,  one  half  this  length  may  con- 
veniently be'  used  for  the  diameter  of  the  crank  circle,  which  is  drawn 
as  shown  in  Fig.  22.  On  this  circle,  the  given  points  of  admission,  cut-off, 
and  compression  are  laid  down  at  K,  P,  and  P4,  respectively,  making  the 
arcs  C — K,  C — P,  and  C — P4  equal,  respectively,  to  the  given  angles  of 
7.5,  105,  'and  60  degrees.  A  line  is  then  drawn  connecting  the  points 
K  and  P,  and,  through  the  center  0  of  the  circle,  a  diameter  is  drawn 
perpendicular  to  this  line,  intersecting  the  crank  circle  in  the  points  A 
and  B  and  the  line  K — P  at  M.  By  measurement,  the  angle  A — 0 — A! 
is  found  to  be  42.5  degrees  and  this  is  the  angle  of  advance  required  to 
be  found.  With  the  lines  0 — A  and  0 — B  as  diameters,  valve  circles  are 
drawn  in  and,  with  0  as  the  center  and  0 — M  as  the  radius,  the  steam- 
lap  circle  is  drawn,  0 — M  being  one  half  the  steam  lap,  which  by  measure- 
ment is  found  to  be  {%  of  an  inch.  The  distance  N — Q  between  the 
intersections  of  the  valve  and  the  lap  circles  with  the  line  0 — C  is  found 
to  be  -fa  of  an  inch,  and  this  is  one  half  the  steam  lead. 

To  find  the  exhaust  lap  and  lead,  draw  from  the  point  P4  a  line  per- 
pendicular to  the  diameter  A — B,  and  intersecting  this  diameter  at  the 
point  M',  the  distance  of  which  from  the  center  0  of  the  crank  circle 
is  the  exhaust  lap,  so  that  the  circle  described  with  0  as  its  center  and 
the  distance  0 — M'  as  a  radius  is  the  exhaust-lap  circle  and  the  distance 


24  VALVE   SETTING 

Q' — N'  between  its  intersection  with  the  line  0 — P3  and  that  of  the 
exhaust- valve  circle  is  found  to  be  -^  of  an  inch,  which  is  one  half  the 
exhaust  lead  of  the  valve;  0 — M'  is  T\  in.,  so  that  the  exhaust  lap  is  J  of 
an  inch. 

2.  A  valve  has  a  travel  of  5  ins.,  a  steam  lap  of  1  in.,  an  exhaust  lap 
of  £  in.,  and  a  steam  lead  of  £  in.  It  is  required  to  find  the  angle  of 
advance  and  the  point  of  cut-off.  The  stroke  of  the  engine  is  4  ft.  and 
the  connecting  rod  is  considered  to  be  of  infinite  length,  so  that  its 


FIG.  22. 

angularity  may  be  disregarded.  It  is  also  required  to  determine  what 
should  be  the  steam  lap  of  the  valve  if  steam  is  to  be  cut  off  at  half 
stroke;  what  should  be  the  angle  of  advance  to  make  the  engine  cut  off  at 
half  stroke,  and  how  this  change  would  affect  the  other  functions  of 
the  valve. 

Here  the  travel  of  the  valve  is  5  ins.,  and  one  half  of  this  may  be 
taken  as  the  diameter  of  the  crank  circle,  which  is  shown  in  Fig.  23 
with  the  two  diameters  C — F3  and  C" — D  at  right  angles.  0 — M — 0 
as  the  center  and  the  radius  0 — M  equal  to  one  half  of  the  given  steam 
lap  of  1  in.,  the  steam-lap  circle  Q  M  L  is  drawn  in,  and  with  a  radius 
of  J  of  an  inch  the  lap  circle  for  the  exhaust  valve  is  also  Hra\ni.  From 
the  point  Q,  where  the  steam-lap  circle  intersects  the  horizontal  diameter 
C — P3,  the  distance  Q — N,  equal  to  J  of  an  inch,  or  one  half  the  given 
steam  lead,  is  laid  off  and,  from  the  point  N,  a  perpendicular  is  erected 


A  STUDY  OF  THE   D   SLIDE   VALVE 


25 


on  the  diameter  C — P3,  intersecting  the  crank  circle  at  the  point  A,  from 
which  the  diameter  A — 0 — B  is  drawn. 

The  angle  A — 0 — C"  is  the  angle  of  advance  and  by  measurement  is 
found  to  be  37  degrees.  Since  the  connecting-rod  length  is  considered 
infinite,  the  distance  of  the  piston  from  the  end  of  its  stroke  at  cut-off 
will  be  equal  to  the  distance  N' — P3  from  the  foot  of  the  perpendicular 
dropped  on  the  diameter  C — Pz  from  the  point  of  cut-off  P.  By  measure- 
ment this  distance  is  found  to  be  f  of  an  inch,  and  since  the  scale  of 
the  diagram  is  2J  ins.  equal  to  the  stroke  of  4  ft.,  the  distance  of  f  of 
an  inch  will  be  exactly  one-fourth  stroke,  so  that  this  is  the  point  of 
cut-off.  This  point  is  found  on  the  diagram  by  drawing  the  line  K — P 


through  the  intersection  of  the  steam-lap  circle  with  the  diameter  A — B 
at  the  point  M,  making  the  line  K — P  perpendicular  to  A — B.  In  this 
way,  also,  the  admission  point  K  is  found. 

To  find  the  amount  of  lap  that  would  be  required  to  make  the  cut-off 
come  at  half  stroke,  assume  the  cut-off  to  be  at  this  point,  or  at  the  line 
0 — C'  in  the  figure,  and  from  C'  draw  a  line  to  the  point  of  admission 
at  K;  0 — A'  is  then  drawn  perpendicular  to  K — C",  and  the  distance 
0 — Mlf  which  by  measurement  is  found  to  be  f  of  an  inch,  is  one  half 
the  steam  lap  that  would  be  required  to  bring  cut-off  at  half  stroke.  With 
this  condition,  the  angle  of  advance  will  be  A' — 0 — C",  which  by  measure- 
ment is  found  to  be  51  degrees.  This  greater  angle  of  advance  would 
make  the  other  movements  of  the  valve  come  earlier  in  the  stroke. 

3.  A  valve  such  as  shown  in  Fig.  24  is  to  have  a  travel  just  sufficient 


26  VALVE   SETTING 

to  open  the  port  wide  for  exhaust,  when  the  exhaust  is  a  maximum,  and 
with  a  connecting  rod  considered  of  infinite  length  it  is  to  cut  off  at 
three  fourths  of  the  stroke.  The  exhaust  port  is  to  begin  opening  when  the 
piston  is  at  one  eighth  of  its  stroke  from  the  end  and  admission  occurs 
at  one  sixteenth  of  the  stroke.  It  is  required  to  find  the  steam  and  ex- 
haust laps,  the  travel  of  the  valve,  the  angle  of  advance  of  the  eccentric, 
and  the  position  of  the  piston  at  exhaust  closure. 

To  solve  this  problem  draw  a  circle,  as  in  Fig.  25,  making  the  diam- 
eter of  any  convenient  length,  which  in  this  case  is  taken  as  3  ins.,  and 
draw  also  the  diameters  C — Pz  and  A' — B'  at  right  angles.  On  the 
diameter  C — P3  the  distance  C — Q  is  2J  ins.,  or  three  quarters  of  the  diam- 
eter. At  this  point  erect  a  perpendicular  to  the  diameter,  intersecting 

the  circle  at  the  point  P,  which  will 
be  the  point  of  cut-off.  In  a  similar 
way  the  point  Q'  is  located,  so  that 
its  distance  from  the  point  P3  is  f 
of  an  inch,  or  one-eighth  stroke  from 
the  outer  dead  center  P3,  and  the 
FJG.  24.  perpendicular  erected  from  this 

point   Qr   intersecting   the  circle   at 

the  point  P'  locates  the  point  of  release.  In  a  similar  way  the  point  N  is 
found  one  eighth  of  the  stroke,  or  %  of  an  inch  from  the  point  C  and 
the  perpendicular  dropped  to  the  circle,  intersecting  it  at  K,  the  point 
of  admission. 

By  connecting  the  points  K  and  P  with  line  K — M — P  and  drawing 
a  diameter  through  the  center  0  perpendicular  to  this  line,  the  angle  of 
advance  A — 0 — A'  is  located  and  this  is  found  to  be  44  degrees.  To 
find  the  point  of  exhaust  closure  or  compression,  draw  from  P'  a  line 
perpendicular  to  the  diameter  A — B  and  intersecting  the  crank  circle  at 
the  point  K',  which  will  be  the  point  of  compression.  By  drawing  from 
this  point  a  line  perpendicular  to  the  diameter  C — P3  and  intersecting 
it  at  the  point  N',  which  is  £  in.  from  (7,  it  is  seen  that  compression  takes 
place  when  the  piston  is  one  sixth  of  its  return  stroke  from  the  inner 
dead  center  C.  Fig.  24  shows  that  the  width  of  the  port  is  2  ins.,  and 
this,  therefore,  is  the  maximum  opening  to  exhaust,  so  that,  according  to 
the  conditions  given  in  Problem  V,  the  travel  of  the  valve  -f-  given  width 
of  port  =  A — B  -T-  M ' — B,  Fig.  25.  The  width  of  the  port  is  2  ins.,  as 
just  stated,  so  that  the  travel  of  the  valve  is  equal  to  2  X  1J  -f-  M' — B, 
which  is  found  by  measurement  to  be  1J|  ins.  This  gives  the  valve  travel 
as  2.13  ins.  (4.26  ins.  actual,  as  the  diagram  is  half  scale),  so  that  all 
linear  dimensions  taken  from  the  diagram  as  drawn  in  Fi^.  •.?.">  must  be 
ivdiirtMl  i?i  th<>  ratio  of  2.1:?  to  :>.  Reducing  the  distance  0 — .17.  which 
measures  §  of  an  inch  by  this  ratio,  we  find  that  the  actual  steam  lap  is 


A   STUDY   OF  THE   D   SLIDE   VALVE 


27 


0.532  in. ;  and  the  exhaust  lap  0 — M ',  reduced  in  a  similar  way  from  its 
actual  measurement  of  •$$  of  an  inch,  gives  the  actual  amount  of  lap  as 
0.133  in. 

4.  In  a  given  engine,  cut-off  is  to  take  place  when  the  crank  is  45 
degrees  from  the  end  of  its  stroke,  release  being  at  15  degrees  from  the 
end  of  the  stroke  and  admission  at  7.5  degrees  from  the  beginning  of 
the  stroke.  The  maximum  exhaust  port  opening  is  2.5  ins.  and  it  is 


required  to  find  the  travel  of  the  valve,  the  steam  and  exhaust  laps,  the 
crank  angle  when  compression  begins  and  the  exhaust  lead. 

Again  making  the  diagram  one  half  full  size,  draw  the  two  lines 
C — P3  and  A' — B'  perpendicular  to  each  other,  as  in  Fig.  26,  and  from 
their  point  of  intersection  0  draw  the  line  0 — K,  making  an  angle  of 
7.5  degrees  with  0 — (7,  also  the  line  0 — P,  making  an  angle  of  45  degrees 
with  0 — P3  and  the  line  0 — Ply  making  an  angle  of  15  degrees  with 
0 — P3.  We  then  lay  off  from  the  point  0  on  the  lines  0 — K  and  0 — P 
equal  distances,  1J  ins.,  as  shown  in  the  figure,  and  connect  the  points 
K  and  P  thus  found.  Through  the  point  0  the  line  A — B  is  drawn 
perpendicular  to  the  line  K — P  and  from  the  point  P',  which  is  also 
1^  ins.  distant  from  0,  the  line  P' — K2  is  drawn  parallel  to  K — P,  so 
that  it  is  also  perpendicular  to  the  line  A — B.  From  its  point 
of  intersection  Mr  with  the  line  A — B,  lay  off  the  distance  1J  ins.  to 


28 


VALVE   SETTING 


the  point  B.  With  0  as  the  center,  and  with  0 — B  as  a  radius,  draw 
the  circle  as  shown.  This  will  be  the  crank  circle  and  its  diameter 
C — P3  the  travel  of  the  valve,  which  hy  measurement  is  found  to  be  3 
ins.  (6  ins.  actual)  while  the  distance  0 — M,  or  the  steam  lap,  is  by 
measurement  found  to  be  £  in.  (1  in.  actual)  and  the  exhaust  lap  0 — M', 
J  of  an  inch  (J  in.  actual),  the  crank  angle  at  compression  C — 0 — 7\T2, 
36  degrees,  and  the  steam  lead  N — Q,  J  in.  on  the  diagram  or  0.5  in. 


actual,  while  the  exhaust  lead  N' — Qr  is  J|  of  an  inch  on  the  diagram 
or  |f  actual. 

It  so  happens  in  this  case  that  the  distance  selected  to  lay  off  on  the 
lines  0 — P  and  0 — K  was  1£  ins.,  or  one  half  the  valve  travel,  but  this 
is  not  necessarily  the  case,  as  the  solution  will  be  unaffected  no  matter 
what  distance  is  laid  off.  Thus,  for  instance,  if  we  should  lay  off  1  in. 
on  0 — P  and  0 — K  to  the  points  K'  and  P'  and  join  these  points  by  a 
line  as  shown,  we  would  still  be  able  to  draw  the  line  A — B  perpendicular 
to  the  dotted  line  so  that  its  angle  with  the  vertical  A' — B'  would  be  the 
same  as  at  first.  All  of  the  linear  dimensions  of  the  diagram  are  deter- 
mined by  the  maximum  opening  to  exhaust,  2£  ins.,  which  is  laid  off 
from  the  poirft  M '  to  B,  as  already  described,  for  determining  the  radius 
for  the  crank  circle. 


Ill 

A    STUDY    OF    THE    ZEUNER    SLIDE-VALVE    DIAGRAM* 

PROBABLY  every  engineer  at  some  time  or  other  has  had  a  nice  job  of 
valve  setting  on  his  hands.  In  fact,  it  is  quite  common  to  hear  an  en- 
gineer begin  a  conversation  with  some  such  remark  as  this:  "Well,  the 
worst  job  I  ever  had  was  to  set  the  valves  on  an  old  high-speed  engine 
with  a  riding  cut-off  valve."  In  another  case  it  may  be  an  experience 
in  setting  the  valves  of  a  double-eccentric  Corliss,  or,  perhaps,  in  still  a 
third  case  it  was  a  tandem  or  cross  compound  engine.  Wherever  one 
goes,  he  is  sure  to  meet  an  engineer  who  is  on  the  lookout  for  a  patent- 
medicine  cure-all  that  will  be  a  sure  preventer  of  the  troubles  met  in  set- 
ting valves.  Perhaps  this  may  not  appear  unusual  when  one  considers  the 
fact  that  on  the  proper  or  improper  setting  of  the  valves  may  depend 
the  balance  of  profit  or  loss  when  it  comes  to  the  final  reckoning  at  the 
end  of  the  year. 

For  those  who  have  mastered  the  principles  of  valve  operation,  the 
work  of  setting  the  valves  is  simple,  but  to  a  large  number  of  engineers 
the  functions  of  the  valve  seem  to  be  hidden  behind  the  valve-chest  cover. 
Even  with  the  cover  removed  and  the  valve  parts  in  plain  sight,  it  is  not 
always  clear  as  to  just  what  changes  are  necessary  to  obtain  a  desired 
result.  In  some  cases  it  is  possible  to  tell  at  a  glance  where  the  trouble 
lies,  but  in  others  one  must  make  a  careful  study  of  the  case,  considering 
the  movements  of  the  valve  in  their  relation  to  the  engine  piston. 

The  making  of  this  analysis  is  not  an  easy  matter  for  those  unfamiliar 
with  mathematical  problems,  and,  although  many  men  can  by  a  few  figures 
or  rule-of -thumb  methods  determine  what  the  valve  conditions  should  be, 
there  are  others  for  whom  the  task  is  not  so  simple.  To  these  men,  ob- 
jects, lines,  and  dimensions  that  are  visible  to  the  eye  make  the  subject 
much  clearer  than  could  be  done  by  the  mazes  of  mathematics  only  suit- 
able for  exploration  by  the  logically  trained  analyst.  It  is,  therefore,  with 
a  view  to  meeting  the  needs  of  the  practical  man,  to  whom  the  chalk 
sketch  tells  everything,  that  this  article  is  written. 

Several  methods  of  graphically  solving  slide-valve  problems  have  been 
worked  out,  but  Zeuner's  diagram  is,  perhaps,  the  most  useful  and  simple 

*  Contributed  to  POWER  by  E.  S-  Hawking. 
29 


30  VALVE  SETTING 

of  all  and  will,  therefore,  be  considered  in  detail.  By  means  of  the  dia- 
gram, the  effect  on  the  steam  supply  of  changes  in  the  dimensions  of  the 
valve,  or  in  the  adjustment  of  the  eccentric,  etc.,  are  made  actually  visible. 

It  is  assumed  that  the  length  of  the  eccentric  rod  is  infinite  or,  in 
other  words,  that  it  moves  in  a  line  parallel  to  the  piston  rod.  This 
assumption  can  safely  be  made,  since  the  angle  due  to  the  eccentric  radius 
is  so  small  as  to  have  no  appreciable  effect  on  the  results.  Given  the 
points  at  which  admission,  cut-off,  etc.,  take  place,  the  diagram  shows  the 
relative  crank  position.  Conversely,  the  position  of  the  valve  correspond- 
ing to  a  given  crank  position  may  be  found  readily.  By  the  use  of  the 
valve  diagram  in  connection  with  the  indicator,  it  is  possible  to  diagnose 
a  case  of  valve  trouble  so  as  to  know  the  dimensions  of  the  valve  and  the 
way  in  which  it  performs  its  functions  as  accurately  and  certainly  as  if 
it  were  seen  operating  within  a  transparent  chest. 

For  the  sake  of  clearness,  let  it  be  supposed  first,  that  the  valve  has 
no  lap  and  that  the  line  0 — Q,  as  in  Fig.  27,  represents  the  eccentric 
radius,  so  that  the  eccentric  travels  in  the  large  circle  as  indicated  by 
the  arrow.  When  it  is  at  Q,  the  valve  is  closed,  but  as  it  moves  around 
the  circle  the  valve  gradually  opens  until,  when  the  eccentric  is  at  the 
point  H,  the  amount  of  opening  is  represented,  to  the  scale  of  the  dia- 
gram, by  the  distance  0 — G.  It  will  be  noted  here  that  the  crank  posi- 
tions are  not  shown,  but  for  any  given  position  of  the  eccentric  in  its 
circle,  the  corresponding  position  of  the  crank  will  be  behind  the  eccentric 
position  by  90  degrees  plus  the  angle  of  advance. 

Since  it  is  desirable  to  avoid  the  necessity  of  dropping  perpendiculars 
to  the  line  of  valve  travel,  such  as  H — G  in  Fig.  27,  it  becomes  necessary 
to  construct  a  line  each  point  of  which  is  distant  from  the  center  0  by 
an  amount  equal  to  the  valve  travel  corresponding  to  the  eccentric  position 
indicated  by  a  line  passing  from  0  through  the  given  point.  To  do  this, 
take  the  point  0  as  a  center  and,  with  0 — G  as  a  radius,  draw  the  arc  G — L 
until  it  intersects  the  line  0 — H.  Then  at  the  position  H'  of  the  eccen- 
tric, drop  the  perpendicular  H' — G'  to  the  line  X — 0 — Y  and,  with  0 — G' 
as  a  radius,  draw  another  arc  intersecting  the  line  0 — //'.  By  continu- 
ing this  process,  a  number  may  be  found  each  of  which  marks  off  on  the 
line  of  eccentric  position  a  distance  from  the  point  0  equal  to  the  valve 
travel  for  the  given  position  of  the  eccentric.  Upon  joining  the  points, 
such  as  L  and  L',  a  closed  curve  is  formed  known  as  the  valve  circle. 

To  prove  that  the  curve  is  a  circle,  take  the  triangles  0 — L — Y — 0 
and  0—G—H—O,  as  in  Fig.  27,  in  which  0—Y  equals  0— H  and  0— G 
equals  0 — L,  while  the  angle  L — 0 — Y  is  common  to  both  triangles. 
Since  the  two  triangles  have  two  sides  and  an  included  angle  equal  the 
one  to  the  other,  they  can  be  placed  in  coincidence  and  are,  therefore, 
equal  the  one  to  the  other,  so  that  the  line  H — G  equals  the  line  L — Y. 


A   STUDY   OF  THE   ZEUNER   SLIDE-VALVE   DIAGRAM 


31 


and  the  angle  0 — L — Y,  being  the  same  as  angle  0 — G — H,  is  a  right 
angle.  The  right  angle  0 — L — Y  being  inscribed  in  the  closed  curve 
and  on  its  diameter  0 — Y,  gives  proof  that  the  curve  is  a  circle. 

Perhaps  it  may  be  thought  that  the  proof  of  the  valve  circle  is  long 
and  unnecessary,  but  it  is  important  to  establish  this  fact  since,  after 
having  done  so,  the  circle  can  be  drawn  in  on  the  eccentric  radius 
as  a  diameter  without  plotting  the  points  as  at  L.  Tnus  the  diagram 
is  simplified  and  the  work  shortened.  By  reasoning  similar  to  what 
has  been  given,  the  valve  circle  for  the  right-hand  end  of  the  valve 
can  be  drawn  in  at  the  left  of  the  figure,  as  in  Fig.  27;  and,  since  the 
valve  is  supposed  to  have  no  laps,  the  two  valve  circles  will -be  identical, 


that  at  the  right  of  the  figure  representing  the  opening  of  the  valve  for 
the  admission  of  steam  at  the  left  while,  at  the  same  time,  the  circle  at 
the  left  of  the  figure  represents  the  opening  of  the  valve  at  the  right 
hand  for  the  escape  of  the  exhaust  steam.  On  the  reverse  stroke  of  the 
piston,  what  was  before  the  circle  for  steam  admission  is  that  for  exhaust 
and  vice  versa.  Thus  in  Fig.  27,  for  the  eccentric  position  J,  the  valve 
will  be  open  for  the  admission  of  steam  at  the  right-hand  end  by  the 
distance  0 — K. 

In  practice,  it  is  not  possible  to  have  a  valve  with  no  lap,  because  if 
such  a  valve  were  constructed  it  could  not  be  closed  tight  enough  to*  pre- 
vent the  escape  of  steam  past  the  edge  of  the  port;  nor  could  the  periods 
of  admission  and  exhaust  be  regulated  to  secure  the  highest  economy. 
Having,  therefore,  drawn  in  the  valve  circle  in  Fig.  28  by  the  process 
already  described,  it  will  be  necessary  to  take  account  of  the  lap  on  the 
two  sides  of  the  valve,  by  drawing  in  the  arcs  C — D  and  A — B  with 
centers  at  the  point  0.  The  distance  0 — C  represents,  to  the  scale  taken, 
the  amount  of  the  steam  or  outside  lap  of  the  valve,  while  the  distance 


32  VALVE   SETTING 

O — A  represents  the  inside  or  exhaust  lap.  When,  therefore,  the  eccen- 
tric is  at  the  position  W,  Fig.  28,  the  amount  the  valve  has  opened  at 
the  left  for  the  admission  of  steam  is  represented  by  the  distance  G — //, 
or  the  sector  0 — //  less  the  length  of  the  steam  lap  0 — G  by  which 
amount  it  is  necessary  for  the  valve  to  travel  before  the  port  opens.  Simi- 
larly, the  distance  / — J  at  the  left  of  the  diagram  is  the  amount  by  which 
the  valve  is  open  for  the  exhaust  of  steam  on  the  right-hand  end  for  the 
same  position  W  of  the  eccentric. 

Usually  it  is  most  convenient  to  refer  all  valve  motions  to  the  posi- 
tion of  the  crank,  since  it  is  easier  to  determine  this  position  than  that 
of  the  eccentric  and,  for  this  reason,  it  is  now  necessary  to  translate  the 
eccentric  positions,  discussed  in  Figs.  27  and  28,  to  the  corresponding 
crank  positions.  This  is  done  in  Fig.  29  by  moving  the  diameter  of  the 
valve  circles  backward  by  an  amount  equal  to  90  degrees  plus  the  angle 
of  advance. 

Suppose  that  the  crank  is  on  the  inner  dead  center,  as  at  C  in  Fig. 
29,  the  corresponding  position  of  the  eccentric  is  at  P  so  that  the  angle 
P — 0 — R  is  the  angle  of  advance.  This  being  the  case,  the  distance 
0 — A  represents  the  amount  of  valve  travel  from  the  mid  position  at 
the  beginning  of  the  stroke.  As  the  crank  revolves  to  the  positions  Cly 
(72,  E3,  etc.,  the  eccentric  moves  through  equal  angles  to  the  correspond- 
ing positions  P19  P2)  P3,  etc.,  .until,  at  this  latter  point,  it  has  had  its 
maximum  effect  on  the  motion  of  the  valve  which  has  now  reached  the  full 
limit  of  travel  to  the  right.  At  this  time,  the  crank  is  evidently  at  the  point 
E3  so  that  the  angle  R — 0 — Ez  equals  the  angle  P — 0 — .R,  or  the  angle  of 
advance.  The  distances  0 — A,  0 — A19  0 — A2,  and  0 — P3  represent  the 
travel  of  the  valve  from  its  mid  position  for  the  various  crank  positions 
C,  C19  C2,  and  Ez.  By  sweeping  circles  from  the  points  A,  A19  A2,  etc., 
to  the  corresponding  points  E,  E19  Ez,  etc.,  with  0  as  a  center  and  con- 
necting Es  with  any  one  of  the  points,  such  as  E19  we  have  a  second 
method  of  proving  the  fact  that  the  valve  curve  is  a  circle,  for,  as  can 
readily  be  seen  in  the  figure,  the  triangle  0 — E^ — E3  is  equal  to  the  tri- 
angle 0— A!— PI. 

As  may  be  inferred  from  what  has  already  been  said,  the  amount 
that  the  valve  overlaps  the  edge  of  the  port  when  in  the  mid  position  is 
called  the  "lap,"  the  part  on  the  outside  of  the  valve  being  known  as 
the  steam  or  outside  lap  while  that  on  the  inside  is  the  exhaust  lap.  Be- 
fore the  steam  port  can  open,  the  valve  must  travel  a  distance  equal  to 
the  amount  of  the  lap  and,  after  it  has  opened,  the  amount  of  opening 
is  always  equal  to  the  amount  of  travel  less  the  amount  of  lap.  This 
fact  has  been  shown  diagrammatically  in  Fig.  28  and  is  also  shown  in 
Fig.  30,  in  which  it  will  be  seen  that  for  the  position  K  the  opening  of 
the  port  is  zero.  This  point,  therefore,  represents  the  crank  position  at 


A  STUDY  OF  THE   ZEUNER   SLIDE-VALVE   DIAGRAM 


33 


the  instant  the  valve  is  ready  to  open  or.,  in  other  words,  the  point  of 
admission.  It  is  evident  from  the  diagram  that  at  the  point  P  the  open- 
ing of  the  valve  is  again  zero,  so  that  this  point  is  the  position  of  the 
crank  when  the  valve  closes  and  cuts  off  the  steam  supply. 

When  the  crank  is  on  the  dead  center,  as  at  C  in  Fig.  30,  the  valve 
is  open  by  the  amount  of  lead,  which  is  represented  in  the  diagram  by  the 
distance  N — Q  on  the  line  of  dead  centers.  In  a  similar  way,  the  amount 
that  the  valve  is  open  to  exhaust  at  the  end  of  the  stroke  is  known  as 
the  exhaust  lead. 

It  is  now  necessary  to  show  the  proof  of  some  of  the  more  important 
properties  of  the  diagram  as  shown  in  Fig.  30.  By  examining  the  figure 
it  will  be  seen  that  a  perpendicular  let  fall  from  the  point  (73,  where  the 


FIG.    29. 


FIG.    30. 


valve-circle  diameter  intersects  the  crank  circle,  cuts  the  line  of  dead  cen- 
ters at  a  point  N  distant  from  the  center  0  by  an  amount  equal  to  the 
lap  plus  the  lead  of  the  valve.  To  prove  that  the  line  joining  the  points 
of  admission  and  cut-off  is  tangent  to  the  steam-lap  circle,  take  the  tri- 
angles C3—0—L  and  P— 0— M,  of  which  the  sides  0— P  and  0— M 
are  equal  respectively  to  the  sides  0 — Cs  and  0 — L,  and  the  angle 
(73 — 0 — P  is  common  to  both  of  the  triangles.  Hence  they  are  equal  and 
the  angle  0 — M — P  equals  the  angle  0 — L — (73,  which  is  a  right  angle, 
thus  proving  that  the  line  P — M — K  is  tangent  to  the  circular  arc 
Q — M — L.  From  this  proposition  it  follows  that  if  a  circle  be  drawn 
with  the  point  C  as  the  center  and  a  radius  equal  to  the  lead,  this  circle 
will  be  tangent  to  the  line  K — P,  which  joins  the  points  of  admission  and 
cut-off.  As  a  proof,  the  line  C — X  is  drawn  from  C  parallel  to  K — P, 
and  therefore  perpendicular  to  (73 — 0,  so  that  the  lines  C — 0  and  (73 — 0 
are  equal,  as  are  also  the  angles  0 — C — X  and  0 — C3 — N.  Since  the 
angle  C — 0 — C3  is  common  to  both  triangles,  they  are  equal  and  X — 0 
=  N—0,  while  X—W^—  N—Q  =  the  lead.  Lines  C— X  and  M—R  are 


34  VALVE   SETTING 

parallel  by  construction,  so  that  C — 72  —  X — M  =  the  lead,  and  C — R — M 
is  a  right  angle  with  the  circle  tangent  to  the  line  K — P. 

Another  property  that  is  useful  in  constructing  the  exhaust  part  of 
the  diagram  when  the  lap  circle  is  so  small  that  it  does  not  give  a  sharp 
intersection  with  the  valve  circle,  is  the  fact  that  if  0 — F  be  drawn  per- 
pendicular to  0 — C3,  and  a  perpendicular  be  let  fall  from  the  point  F 
on  the  admission  line,  it  will  be  equal  in  length  to  the  radius  of  the 
steam-lap  circle.  The  truth  of  this  proposition  is  readily  seen  from  the 
fact  that  the  triangles  F — 0 — Y  and  0 — K — M  are  equal,  because  they 
have  equal  hypotenuses  and  are  right-angled  triangles  with  the  angles 
F — 0 — Y  and  M — K — 0  equal.  Lines  F — Y  and  0 — M  being  similar 
sides  of  equal  triangles  are  themselves  equal. 

To  construct  the  part  of  the  diagram  corresponding  to  the  exhaust  side 
of  the  valve,  the  reasoning  is  the  same  as  that  just  given  for  the  steam 
side,  the  piston  being,  however,  on  the  return  stroke  from  P3  to  C,  in 
Fig.  29,  so  that  the  valve  circle  comes  in  the  lower  half  of  the  figure. 
The  angle  of  advance  and  travel  of  the  valve  are  the  same  as  for  the 
steam  side  of  the  diagram,  but  the  lap  is  somewhat  less,  since  economical 
performance  requires  as  small  a  lap  as  possible,  and  the  lower  steam  pres- 
sures usually  prevailing  on  this  side  of  the  valve  make  it  possible  to  have 
a  tight  seating  valve  without  a  great  amount  of  lap.  The  exhaust  lead 
and  the  points  of  release  and  compression  correspond  respectively  to  the 
steam  lead  and  the  points  of  admission  and  cut-off,  and  are  obtained  on 
the  exhaust-valve  circle  in  the  same  manner  as  the  corresponding  points  of 
the  steam-valve  circle. 

Fig.  31  shows  a  complete  diagram,  in  which  admission  takes  place  at 
A,  as  represented  by  the  angle  A — 0 — X,  while  cut-off  takes  place  at  C, 
as  given  by  the  angle  C — 0 — X.  In  this  figure,  the  steam  lap  and  steam 
lead  are  represented  respectively  by  the  distances  0 — N'  and  N' — N. 

In  practical  construction,  it  is  not  possible  to  have  a  steam  port  wide 
enough  to  give  full  opening  to  the  exhaust,  so  that  the  width  of  this  port 
must  be  marked  off,  as  in  the  figure,  by  the  arc  W — W,  the  length  of 
the  line  L — W  representing  to  scale  the  width  of  the  port  so  that  the 
exhaust  port  is  open  wide  when  the  crank  is  in  the  position  0 — W,  and 
remains  open  until  it  reaches  the  position  0 — W.  If  this  same  width 
of  the  steam  port  be  laid  off  in  addition  to  the  lap  on  the  diameter  of 
the  steam  valve  circle,  the  point  for  the  port  to  be  wide  open  will  fall 
at  E'  in  the  figure,  thus  showing  that  this  port  can  never  be  fully  open 
since  the  distance  0 — E'  that  the  valve  would  have  to  travel  is  greater 
than  its  maximum  displacement. 

From  this  it  is  to  be  seen  that  when  the  valve  has  moved  to  give  the 
>t<  ;ini  port  its  maximum  opening,  the  left-hand  end  of  the  valve  overlaps 
the  right-hand  cud  <>f  the  port  by  an  amount  equal  to  the  distance  E — E' 


A  STUDY  OF   THE   ZEUNER   SLIDE-VALVE   DIAGRAM 


35 


in  the  figure.  Fig.  31  is  the  diagram  for  the  head  end  of  the  cylinder, 
the  diagram  for  the  crank  end  being  similar.,  with  the  exception  that  the 
laps  are  different. 

In  Fig.  31  is  shown  the  probable  form  of  indicator  diagram  that  would 
be  obtained  from  an  engine  represented  by  the  valve  diagram  shown.  The 
points  of  admission,  cut-off,  dead  center,  release,  compression,  etc.,  of  the 
valve  diagram  are  projected  down  to  the  corresponding  points  of  the  in- 
dicator diagram.  A  base  line  is  then  established,  and  the  probable  line 


FIG.    31. 

of  vacuum  is  laid  off  on  a  vertical  scale  of  pressures  on  which  the  boiler 
and  admission  pressures  are  also  laid  off  at  proper  height  for  the  assumed 
boiler  pressure  available.  In  this  way,  the  points  where  the  curvature  of 
the  diagram  boundary  changes  are  determined,  and  smooth  curves  are 
sketched  in  by  eye  to  make  connections. 

Diagrams  of  this  kind  are  of  service  principally  in  designing  the  en- 
gine, but  they  may  be  of  considerable  use  in  every-day  work,  by  showing 
approximately  what  shape  the  diagram,  taken  with  the  indicator,  should 
have.  This  is  especially  the  case  with  high-speed  engines  with  which  it  is 
often  difficult  to  know  whether  or  not  the  diagram  taken  with  the  indi- 
cator represents  the  actual  performance  of  the  engine.  In  some  cases  there 
are  forces  at  work  which  distort  the  diagram  of  the  high-speed  engine 


36  VALVE   SETTING 

until  it  is  difficult  to  recognize  the  different  valve  operations.  Sometimes 
the  freaky  diagrams  are  the  result  of  irregular  expansion  and  contraction 
of  the  valves,  ports,  and  steam  passages,  with  the  engine  at  different  tem- 
peratures, as  after  running  some  time  or  when  just  starting  up. 

Altogether,  there  are  twelve  points  of  information  given  by  the  kind  of 
valve  diagram  shown  in  Fig.  31,  those  not  already  mentioned  being  the 
angle  of  advance  E — 0 — U;  the  travel  of  the  valve  X — 0 — Y\  release 
at  By  given  by  the  angle  B — 0 — Y  \  compression  at  D,  given  by  the  angle 
D — 0 — X;  the  exhaust  lap  0 — L\  the  exhaust  lead  F' — // ;  and  the  maxi- 
mum opening. 

In  any  consideration  of  the  valve  by  the  diagram,  it  is  necessary  that 
the  points  of  admission  and  cut-off,  as  well  as  the  point  of  compression 
and  the  exhaust  lap,  be  given  in  terms  such  that  they  may  be  laid  down 
on  the  diagram  by  angular  distances  of  the  crank  from  the  beginning  or 

end  of  the  stroke.  If,  as  is  some- 
times the  case,  these  items  of  in- 
formation are  given  as  taking  place 
at  a  certain  part  of  the  stroke,  it 
will  be  necessary  to  find  the  angular 
positions  corresponding  to  the  data 
given  by  drawing  a  crank  circle  or 
a  circle  of  reference  on  a  new 
scale.  In  doing  this,  it  is  most 
convenient  to  draw  the  circle  con- 
centric to  the  valve  diagram. 
FIG.  32.  As  an  example,  suppose  that  the 

cut-off  is  given  as  at  five  eighths  of 

the  stroke;  the  crank  circle  is  then  drawn  as  in  Fig.  32,  so  that  the  dis- 
tance C — F3  represents,  to  the  selected  scale,  the  stroke  of  the  engine. 
The  distance  C — A  is  then  laid  off  equal  to  five  eighths  of  C — P3  and 
with  a  radius  corresponding,  by  the  selected  scale,  to  the  length  of  the 
connecting  rod  and  with  the  center  at  B,  an  arc  is  swept  from  A  to  P. 
The  angle  C — 0 — P  thus  formed  is  the  angular  distance  from  the  begin- 
ning of  the  stroke  at  which  cut-off  takes  place.  This  angle  is  then  trans- 
ferred to  the  valve  diagram  and  any  remaining  angular  distances  still 
unknown  are  found  and  transferred  in  the  same  manner. 

It  will  be  noted  that  the  different  points  of  information  given  by  the 
diagram  appertain  part  to  the  steam  side  and  the  others  to  the  exhaust 
side  of  the  valve,  while  the  angle  of  advance  and  the  valve  travel  are 
common  to  both  sides.  In  order  to  construct  a  complete  diagram,  it  is 
necessary  that  four  of  these  points  of  information  be  given,  although  for 
the  construction  of  either  the  steam  or  exhaust  side  alone  three  points 
will  be  sufficient.  Where  the  complete  diagram  is  to  be  constructed,  one 


A   STUDY  OF   THE   ZEUNER  SLIDE-VALVE   DIAGRAM  37 

or  two  of  the  points  given  must  belong  to  a  different  side  of  the  diagram 
from  the  others,  and  one  of  the  points  must  be  a  linear  measurement,  such 
as  the  steam  lap,  steam  lead,  or  maximum  opening;  otherwise,  as  can 
readily  be  seen,  the  angular  measurements  could  be  used  to  construct  a 
valve  of  any  given  linear  dimensions  provided  only  that  the  different 
measurements  bear  a  certain  relation  to  each  other.  Since  the  opening 
to  exhaust  is  greater  than  that  to  steam,  and  since  the  ports  can  only  be 
made  sufficiently  wide  to  allow  full  opening,  the  width  of  port  when  given 
as  part  of  the  data  in  any  problem  may  be  taken  as  the  maximum  opening 
of  the  exhaust  port. 


IV 


THE    RIDING    CUT-OFF    VALVE 

THIS  chapter  has  to  deal  with  what  is  known  as  the  Meyer  cut-off  valve 
of  which  there  are  in  use  a  few  different  modifications  of  design,  such 
as:  (a)  Single  valve  and  cut-off  set  over  the  ports  in  a  midposition  be- 
tween the  ends  of  the  cylinder;  (b)  valves  bridging  ports  at  each  end 
of  the  cylinder  operating  as  one;  (c)  separate  valves  over  each  steam 
valve  port,  and  separate  valves  over  the  steam  and  exhaust  cylinder  ports. 

The  cut-off  valve  operating  in  conjunction  with  the  main  steam  valve, 
or  valves,  may  be  riding  over  or  inside  cut-off,  but  the  action  must  be  the 
same  in  principle.  The  only  difference  is  that  with  more  valves  used  a 


FIG.    33. 


FIG.    34. 


shorter  steam  port  and  independent  and  closer  adjustment  of  action  is 
secured. 

It  is  the  purpose  of  this  chapter  to  treat  only  of  the  simplest  of  Meyer 
cut-off  valves,  of  which  Fig.  33  is  an  illustration.  This  valve  may  be  so 
constructed  and  connected  that  it  may  cut  off  the  steam  at  a  fixed  and 
unvarying  point,  or  by  means  of  a  hand  wheel  vary  that  point,  to  offset 
variations  in  boiler  pressure,  as  in  marine  work;  or  where  regularity  of 
speed  is  essential,  the  cut-off  valve  may  be  operated  from  a  shaft  or  other 
governor,  the  main  valve  being  operated  from  a  fixed  eccentric. 

In  the  case  under  discussion  the  main  valve  and  the  cut-off  valve  are 
each  driven  by  a  separate  fixed  eccentric.  The  resemblance  of  the  Meyer 
cut-off  valve,  in  this  connection,  to  the  D. slide  valve  is  shown  by  compar- 
ing Figs.  33  and  34. 

The  main  valve  of  the  Meyer  combination,  Fig.  33,  controls  the  lead, 


THE  RIDING  CUT-OFF   VALVE 


39 


latest  point  of  cut-off,  the  exhaust,  and  the  compression.  The  cut-off 
valve  controls1  the  point  at  which  expansion  shall  begin.  Comparing  the 
two  valves  placed  in  mid-position  of  their  travel,  it  will  be  seen  that  the 
edge  h  of  the  main  valve  will  cut  off  the  steam  from  the  cylinder  the 
same  as  the  edge  K  of  the  common  slide  valve,  Fig.  34.  Also,  the  edge 
J  of  the  one  valve  should  act  the  same  as  the  edge  J  of  the  other,  pro- 
viding the  eccentrics  are  in  the  same  relative  positions.  The  same  applies 
to  the  exhaust  edges  of  each  valve,  M  and  N.  The  edge  h  will  cut  off 
steam  from  the  port  &  independently  of  any  action  of  the  cut-off  valves. 

The  longest  distance  at  which  steam  is  admitted  is  controlled  by  the 
main  valve,  and  the  work  of  the  cut-off  valve  is  to  cut  off  steam  at  some 
earlier  point  in  the  stroke.  This  it  does  by  the  edge  G  of  the  cut-off 
passing  over  the  edge  g  of  the  port  L,  and  on  the  other  stroke  the  edge  n 
of  the  cut-off  passing  over  the  edge  n  of  the  port  K. 

ACTION  OF  THE  VALVES 

For  example,  let  the  steam  ports  be  1  in.  wide,  both  in  the  vaive  and 
the  cylinder,  and  the  main  valve  have  a  steam  lap  of  J  in.,  which  will 
give  the  main  valve  a  cut-off  at  about  nine  tenths  of  the  stroke;  and  if 
the  travel  of  the  main  valve  be  just  sufficient  to  open  fully  the  steam 
ports,  the  action  of  the  main  valve  will  not  be  unduly  distorted  by  ex- 
cessive lap  or  over  travel.  Assuming  that  the  main  steam  valve  and  cut-off 
valve  when  in  midposition  leave  the  edges  n  and  G  of  the  cut-off  valve 
equidistant  from  the  nearest  edges  of  the  main  valve,  i.e.,  one  half  the 
width  of  the  steam  port,  take  these  as  average  conditions  and  follow  the 
movements  as  follows: 

In  Fig.  35,  the  crank  (the  travel  being  represented  by  the  circle),  is 
on  its  dead  center  at  the  crank  end  B,  the  cut-off  eccentric  in  this  ex- 


FIG.    35. 


ample  being  set  exactly  opposite  at  N  and  the  main  eccentric  at  M,  the 
main  valve  having  no  lead.  It  will  be  seen  that  the  valves  moving  in  the 
direction  denoted  by  their  arrows,  while  the  crank  starts  in  the  direction 
shown  by  its  arrow,  the  admission  of  steam  will  occur  through  the  ports 
K  and  a  uninfluenced  by  the  cut-off  valve. 


40 


VALVE   SETTING 


Fig.  36  shows  the  position  of  the  valves,  eccentrics,  and  crank  at  the 
point  of  cut-off.  The  crank  being  at  half  stroke,  the  cut-off  is  performed 
by  that  valve  independently  of  the  action  of  the  main  valve. 


FIG.    36. 

Fig.  37  shows  the  position  of  the  valves  and  eccentrics  at  the  point 
of  exhaust  release  on  the  same  end  from  the  port  a,  thus  completing  the 
action  of  the  valves  for  one  piston  stroke. 

Fig.  38  represents  the  same  valves  at  one  point  in  the  processes  shown 
in  the  previous  figures.  It  is  to  illustrate  the  point  that  the  effective  area 


FIG.    37. 


of  admission  of  steam  through  the  valve  port  K  to  the  cylinder  port  a 
is  governed  by  the  action  of  the  cut-off  valve. 

In  this  case,  where  the  eccentrics  are  set  as  they  are,  the  cut-off  valve 
moves  across  the  main  valve  port  K  before  the  latter  valve  has  cut  off, 


I/ 

O  \! 


FIG.    38. 


FIG.    39. 


thus  reducing  the  effective  port  area.  This  condition  must  be  considered 
to  obtain  the  most  effective  use  of  the  valves  and  a  change  in  position  of 
eccentrics  to  get  the  quickest  action  of  the  valves  at  the  proper  time  is 
desirable. 

Eccentrics  are  set  as  in  the  foregoing  examples  mostly  on  engines 


THE  RIDING  CUT-OFF   VALVE 


41 


where  a  reversing  of  direction  of  rotation  is  wanted.  But  where  the  direc- 
tion of  travel  is  constant,  a  greater  latitude  of  position  of  the  eccentric 
is  allowed  and  taken  advantage  of  in  greater  or  lesser  degree  by  various 
builders.  Assume  that  we  still  have  valves  with  the  same  amount  of  lap, 
etc.,  as  already  shown,  and  study  the  effects  of  change  of  position  of  the 
eccentric  by  a  few  more  illustrations. 

In  Fig.  39  the  circle  represents  the  travel  of  the  crank  and  eccentrics. 
The  crank  is  on  dead  center  B,  ready  to  start  in  the  direction  of  the 
arrow;  0  is  the  throw  line  of  the  crank  N  of  the  cut-off  eccentric  and 
M  of  the  main  eccentric,  N  being  169  degrees  ahead  of  the  crank  and  59 


FIG.   40. 


degrees  ahead  of  the  main  eccentric,  the  angular  advance  of  which  is  20 
degrees. 

Fig.  40  represents  the  position  of  the  valves  and  eccentrics  at  the  point 
of  cut-off.  Bearing  in  mind  the  position  of  the  eccentrics  before  illus- 
trated, note  the  action  of  the  same  as  shown  in  this  figure.  In  passing 
the  point  X  the  eccentric  moves  the  valve  quickest  on  this  stroke.  It  will 
then  be  seen  that  the  cut-off  valve  has  moved  its  fastest  while  near  cut-off 
and  the  eccentric  was  passing  this  point;  at  the  same  time  the  main  valve 
has  not  come  to  its  best  speed. 

Then  noting  Fig.  41,  which  shows  the  relative  positions  at  point  of 
cut-off  of  the  main  valve,  it  is  seen  that  the  two  valves  have  been  travel- 


FIG.    41. 


ing  at  nearly  the  same  speed  while  making  the  cut-offs,  with  the  cut-off 
valve  going  the  fastest  at  the  right  point  and  slower  than  the  main  valve 
after  the  latter  has  closed  the  cylinder  port,  thus  shutting  out  the  possibil- 
ity of  reopening  by  the  main  valve's  catching  up  and  passing  the  cut-off 
before  the  main  valve  has  cut  off. 


42  VALVE  SETTING 

The  main  valve  is  traveling  faster  in  Fig.  41  for  the  added  reason  that 
it  travels  faster  while  the  eccentric  is  moving  up  to  the  point  X  than 
after  it  leaves  it,  for  any  given  distance  of  the  eccentric  travel  on  that 
stroke.  To  illustrate  this  point,  refer  to  Fig.  42,  in  which  the  circle  rep- 
resents the  eccentric  travel,  the  line  L — L  the  line  of  valve  travel,  N  the 
position  of  the  eccentric  35  degrees  ahead  of  the  point  X,  and  N  the  posi- 
tion of  the  eccentric  35  degrees  the  other  side. 

Setting  a  pair  of  compasses  to  represent  the  length  of  the  eccentric 
rod,  place  one  point  at  M  and  mark  on  the  line  L — L  the  arc  0 ;  next 
set  one  point  at  X  and  scribe  the  arc  P;  then  with  one  point  at  N,  scribe 
arc  Q.  The  distance  from  0  to  P  is  the  distance  the  valve  traveled  while 
the  eccentric  moved  from  M  to  X,  and  the  distance  from  P  to  Q  is  the 
distance  the  valve  traveled  while  the  eccentric  moved  from  X  to  N.  The 
difference  in  valve  travel  while  the  eccentric  traveled  equal  distances  from 
X  is  shown  by  the  arc  r.  This  will  illustrate  why  the  cut-off  valve  must 


FIG.   42.  FIG.   43. 

travel  at  least  as  fast  as  the  main  valve  from  the  position  shown  in  Fig. 
40  to  that  shown  in  Fig.  41. 

Now  comes  the  question  of  length  of  the  eccentric  rod.  Assuming  that 
in  all  the  cases  spoken  of  in  this  article  an  engine  of  20-in.  stroke  were 
used,  it  will  be  found  that  in  the  case  of  setting  the  cut-off  eccentric 
exactly  opposite  to  the  crank,  the  cut-off  of  steam  occurred  at  9  ins.  of 
both  strokes,  while  in  the  case  where  the  cut-off  eccentric  was  set  back 
11  degrees  in  Fig.  39  the  cut-off  of  steam  is  delayed  to  the  thirteenth  inch 
of  one  stroke  and  the  sixteenth  inch  of  the  other,  delaying  the  cut-off  in 
both  strokes  and  making  it  unequal.  The  additional  reason  for  this  latter 
condition  is  that  in  this  case  the  cut-off  eccentric  has  been  set  back  and 
its  rod  made  of  such  length  as  to  get  the  longest  point  of  cut-off  without 
a  reopening. 

To  equalize  the  points  of  cut-off  it  is  necessary  to  move  the  cut-off 
eccentric  back  more  and  shorten  the  rod.  In  Fig.  43,  for  example,  iho 
positions  of  the  valves  are  shown  at  the  time  the  piston  is  on  the  thirteenth 
inch  of  its  motion  on  the  back  stroke  (lhi<  being  the  point  of  cut-off  for 
the  other  stroke),  and  it  is  shown  that  the  steam  port  L  is  not  yet  closed. 
If,  to  close  it,  the  cut-off  eccentric  be  moved  ahead,  it  will  hasten  the. 
point  of  cut-off  for  the  other  stroke,  and  if  we  lengthen  the  rod  to  close 


THE   RIDING  CUT-OFF   VALVE 


43 


L,  it  will  delay  the  point  of  cut-off  for  the  other  stroke,  and  that  would 
in  this  case  cause  a  reopening. 

The  course  to  pursue  is  to  change  the  position  of  the  eccentric  and 
the  length  of  the  rod  as  well,  adjusting  the  two  until  the  ports  just 
escape  reopening  and  the  cut-off  is  equal.  In  this  way  the  longest  possible 
equalized  points  of  cut-off  are  obtained. 

Allowing  that  in  every  change  of  position  of  the  cut-off  eccentric  a 
corresponding  change  of  length  of  rod  must  be  made:  Referring  back  to 
Fig.  40,  with  eccentrics  set  as  here  (and  the  two  valves  moving  together 
after  the  point  of  cut-off),  the  cut-off  valve  will  not  act  on  the  forward 
stroke  after  the  thirteenth  inch  of  piston  stroke,  and  since  the  main  valve 
cuts  off  after  the  eighteenth  inch  of  the  stroke,  therefore  no  cut-off  can  be 
effected  between  these  points. 

That  this  cannot  be  remedied  by  moving  the  cut-off  eccentric  may  be 
shown  as  follows :  Referring  again  to  Fig.  40,  if  the  cut-off  eccentric  were 
moved  farther  ahead,  increasing  its  angle  of  169  degrees,  the  cut-off 
would  occur  earlier,  while  if  the  angle  were  diminished,  the  cut-off  would 
not  be  effected  by  the  cut-off  valve,  because  it  would  not  fully  cover  the 
port. 

This  will  be  seen  by  reference  to  Fig.  44,  in  which  the  cut-off  eccentric 
is  moved  closer  to  X,  and  as  a  result  the  cut-off  is  effected  by  the  main 


FIG.    44. 


valve.  Finally  if  the  cut-off  eccentric  were  moved  to  the  position  X,  Fig. 
45,  at  the  time  the  main  eccentric  stood  at  M,  the  cut-off  valve  would  not 
effect  the  cut-off  at  all.  The  cut-off  eccentric  is  thus  shown  to  be  in  posi- 
tion to  cut  off  at  the  latest  possible  point,  without  reopening  the  port,  as 
shown  in  Fig.  40. 

Having  limited  the  position  of  the  cut-off  eccentric  in  one  direction, 
the  next  step  is  to  find  how  far  it  can  be  set  to  cut  off  as  early  in  the 
stroke  as  possible. 

In  the  foregoing  examples  the  cut-off  was  set  at  180  degrees  from  the 
crank,  or  at  a  lesser  angle  ahead  of  the  crank,  but  it  may  be  set  at  some 
angle  behind  the  crank  instead  of  ahead  of  it.  It  is  understood  that 
ahead  means  less  than  180  degrees  ahead  of  the  crank  in  the  direction 


44 


VALVE   SETTING 


of  rotation,  and  behind  the  crank  is  less  than  180  degrees  in  the  direction 
opposite  the  direction  of  rotation  from  the  crank. 

In  Fig.  46,  for  instance,  it  is  set  at  90  degrees  behind  the  crank,  the 
valve  lap  and  travel  remaining  the  same  as  before,  the  crank  B  on  "  dead 


x€) 


FIG.    46. 


center,"  the  main  valve  having  no  lead,  and  the  port  a  being  closed.  In 
Fig.  47  are  shown  the  positions  at  the  point  of  cut-off,  the  crank  having 
moved  but  22  degrees. 


FIG.    47. 


On  continuing  the  motion,  the  ports  will  arrive  at  the  position  shown 
in  Fig.  48,  from  which  it  will  be  seen  that  the  cut-off  eccentric  being 
at  N,  and  the  main  eccentric  at  M,  and  the  crank  at  B,  the  movements 
of  the  two  valves  would  be  in  opposite  directions.  The  cut-off  valve  will, 
therefore,  keep  the  port  K  closed  until  the  valves  again  change  direction 
and  approach  the  positions  shown  in  Fig.  46;  and  it  is  clear  that  if  the 


FIG.    48. 


cut-off  eccentric  were  set  at  less  than  90  degrees  behind  the  crank,  the 
cut-off  valve  would  first  effect  the  cut-off,  then  lag  behind  and  reopen 
the  port  K.  In  Fig.  49,  for  example,  the  cut-off  eccentric  has  been  ad- 
vanced to  86  degrees  behind  the  crank,  and  the  cut-off  valve  after  having 


THE   RIDING  CUT-OFF   VALVE  45 

cut  off  the  steam  lags  behind  and  has  begun  its  return  stroke,  allowing 
the  ports  to  reopen  and  live  steam  to  reenter,  as  denoted  by  the  arrow. 
Therefore,  the  least  possible  angle  behind  the  crank  for  a  cut-off  valve 
is  90  degrees.  These  are  the  principal  points  to  be  understood  and  should 
be  quickly  grasped  when  ready  to  set  these  valves. 

The  ranges  of  angle  of  advance  for  both  the  main  and  cut-off  valves 
here  given  are  the  maximum  in  either  direction.  In  engineering  prac- 
tice, various  builders  vary  the  amount  of  advance  and  valve  lap,  but  it 
is  within  this  range.  Some  designers  have  less  lap  than  herein  given, 
say  25  per  cent,  of  lap,  and  so  adjust  the  position  of  the  eccentrics  that  the 
cut-off  will  conform  to  the  condition  of  the  lap.  In  a  multiported  cut-off 


FIG.    49. 

valve  is  exhibited  the  greatest  degree  of  perfection,  as  it  gives  a  maximum 
opening  with  a  minimum  lap. 

It  is  not  the  writer's  purpose  to  go  too  deeply  into  the  design  of  this 
valve,  only  just  sufficiently  to  set  the  valves  with  the  hints  that  follow. 
Before  going  further,  however,  it  is  well  to  dwell  on  the  principal  points 
already  brought  out : 

First,  all  classes  of  the  Meyer  cut-off  valve  are  similar  in  action  to 
the  D  slide  valve,  and  easier  to  set  for  complicated  conditions. 

Second,  Figs.  35,  36,  37,  and  38  have  to  deal  with  single  valves  and 
eccentrics,  with  the  cut-off  set  exactly  opposite  the  crank.  Such  valve 
and  eccentric  arrangement  is  found  mostly  on  marine  engines,  sometimes 
using  a  hand  wheel.  The  use  of  the  hand  wheel  on  the  valve  stem  gives 
the  effect  of  more  or  less  lap. 

Third,  where  the  direction  of  rotation  is  constant,  and  especially  in 
stationary  practice,  a  modification  of  the  position  of  the  cut-off  eccentric 
is  more  desirable  and  is  varied,  as  shown  by  Figs.  39,  40,  41,  42,  43,  44, 
45,  46,  47,  48,  and  49.  Where  the  lap  is  50  per  cent,  of  the  port,  the 
following  facts  are  to  be  remembered  in  locating  the  position  of  the  eccen- 
tric: That  to  get  a  cut-off  later  than  one-half  stroke,  the  eccentric  must 
be  set  less  than  180  degrees  before  the  crank  down  to  169  degrees  before 
the  crank  (no  less),  as  shown  in  Figs.  39,  40,  and  41.  To  get  a  cut-off 
>at  earlier  than  one-half  stroke,  the  eccentric  must  be  set  at  less  than  180 
degrees  behind  the  crank,  down  to  90  degrees  behind  the  crank  (no  less), 
as  shown  in  Figs.  43,  44,  45,  46,  47,  48,  and  49. 


46 


VALVE  SETTING 


Fourth,  the  multiported  valves  may  change  this  so  that  in  some  cases, 
with  small  lap,  an  early  cut-off  may  be  secured  with  the  eccentric  less 
than  180  degrees  ahead. 

Fifth,  in  engines  equipped  with  multiported  valves,  the  length  of  rods, 
eccentric  travel,  and  valve  lap  are  all  attended  to  by  the  designer,  so  that 
the  essential  for  the  engineer  in  charge  (after  wear  has  set  in  and  slipped 
eccentrics  are  a  possibility)  is  to  know  the  proper  position  of  the  eccen- 
tric and  how  to  locate  that  point  practically  with  all  the  gear  mounted  on 
the  engine. 

Sixth,  with  all  cut-off  valve  gear  the  main-valve  action  is  first  looked 
into,  and  its  action  is  to  be  considered  the  same  as  in  any  D  slide  valve. 
Then  the  cut-off  valve  is  to  be  considered  as  the  steam  edges  only. 


To  SET  THE  VALVES 

On  all  engines,  when  preparing  to  set  the  valves,  the  first  thing  is  to 
find  and  adjust  all  lost  motion  in  the  valve  gear,  then  proceed  to  place 
the  engine  on  the  "dead  center."  Owing  to  the  fact  that  the  crosshead 
will  remain  stationary  a  short  time  before  the  crank  pin  passes  the  center, 
and  remain  so  until  the  crank  has  passed  the  center  a  short  distance,  it 
is  best  to  take  greater  care  than  to  simply  note  the  point  where  the  cross- 


FIG.  so. 

head  rests  at  the  end  of  the  stroke,  in  order  to  find  the  "dead  center." 
The  writer  believes  the  process  illustrated  in  Fig.  50  is  an  accurate  process. 
In  the  figure,  J  and  K  represent  two  crosshead  guides,  L  the  cross- 
head,  M  the  path  of  crank  travel,  N  and  0  the  center  lines  of  the  con- 
necting rod  at  different  positions,  and  P  the  balance  wheel.  To  start 
with,  make  a  tram  8  out  of  any  material  convenient,  preferably  round 
steel.  Turn  the  engine  around  until  the  crank  is  at  the  point  B  in  any 
position  where  the  crosshead  is  still  moving  with  the  other  parts,  near  tin* 
end  of  the  stroke.  Then  place  mark  A  on  the  crosshead,  running  the 


THE  RIDING  CUT-OFF   VALVE  47 

mark  up  close  to  nearest  or  most  convenient  guide  bar.  (Where  the 
crosshead  is  down  in  the  frame  of  the  engine,  use  a  straight  edge  across 
the  top  of  the  holding-down  bars.)  Then  place  mark  C  on  the  guide  bar 
opposite  the  mark  A  on  the  crosshead.  Now,  with  the  tram  8  (one  point 
on  the  given  mark  on  the  floor  opposite  the  fly  wheel,  and  on  a  line  with 
one  edge  of  the  rim)  scribe  the  mark  D  on  the  face  or  side  of  the  rim, 
making  the  arc  come  to  the  edge  in  either  case. 

Next  turn  the  engine  so  that  the  crank  passes  the  center  and  the 
mark  A  on  the  crosshead  again  comes  to  the  mark  (7  on  the  guide  bar. 
Then  take  the  tram,  again  resting  it  on  the  same  point  on  the  floor,  and 
scribe  the  arc  to  the  mark  F  on  the  same  edge  of  the  rim  of  the  wheel. 
The  crank  will  then  be  at  E. 

Now  place  prick-punch  marks  as  near  the  edge  as  possible  at  the  points 
D  and  F,  and  with  a  pair  of  dividers  bisect  the  distance  from  D  to  F  and 
make  the  mark  G.  Turn  the  engine  back  so  that  with  the  tram  resting 
at  the  same  point  on  the  floor,  the  other  point  of  the  tram  will  touch  G. 
The  crank  will  then  be  on  "  dead  center  "  at  I,  and  the  mark  A  on  the 
crosshead  will  be  opposite  the  mark  H  on  the  guide  bar,  which  should 
be  marked  as  the  point  where  the  crosshead  reaches  the  end  of  the  stroke. 

Turn  the  engine  to  the  opposite  end  of  the  stroke  and  repeat  the  fore- 
going moves,  when  both  "  dead  centers  "  will  have  been  found  and  marked. 
Now,  with  a  marking  chisel  go  over  all  the  scribe  marks  and  make  them 
permanent,  and  where  the  center  punch  marks  are  on  the  rim  of  the  wheel, 
the  floor  and  the  frame,  it  is  a  wise  precaution  to  place  marks  like  this 
^]  around  the  center  punch  marks.  It  is  also  a  good  means  of  finding 
the  marks  in  future. 

The  next  move  is  to  get  the  eccentric  on  "dead  center."  Where  the 
eccentrics  are  fastened  by  set-screws,  friction  keys,  or  keys  easily  with- 
drawn, loosen  up  on  one  or  the  other,  as  the  case  may  be,  and  turn  the 
eccentric  around  the  shaft  while  finding  the  centers.  Where  there  is  a 
fixed  eccentric,  as  in  governor  eccentrics,  the  engine  itself  must  be  turned 
around  to  find  the  points  desired. 

Make  a  tram  A,  Fig.  51,  out  of  a  board  or  sheet  steel  and  place  at  the 
point  indicated  a  nail  or  other  pointed  iron  or  steel,  just  far  enough  out 
so  that  arcs  B  C  and  D  E  can  be  scribed,  bringing  the  arcs  down  to  the 
edge  of  the  eccentric  at  the  points  B  and  D.  Care  should  be  exercised, 
in  using  the  tram,  to  have  the  end  on  the  shaft  or  the  boss  of  the  eccen- 
tric the  same  distance  away  from  the  eccentric  in  both  instances.  Take 
a  pair  of  dividers  and  from  the  points  B  and  D  scribe  arcs  so  that  they 
will  exactly  intersect  on  the  eccentric  edge  at  F.  This  will  be  the  center 
line  of  the  eccentric. 

Make  another  tram  G,  Fig.  52,  make  a  mark  H  with  the  center  punch 
on  the  eccentric  rod,  and  with  one  leg  of  the  tram  on  the  point  H  scribe 


48 


VALVE  SETTING 


the  arcs  J  K  and  L  M  on  the  eccentric  strap  coming  to  the  points  J  and  L 
on  the  edge  of  the  strap.  With  the  dividers  scribe  from  points  J  and  L 
arcs  exactly  intersecting  each  other  at  the  point  N. 

With  a  marking  chisel  make  permanent  marks  at  the  point  F  on  the 
eccentric  and  the  point  N  on  the  eccentric  strap.     Bring  the  eccentric 


FIG.    51. 


around  so  that  both  points  correspond  and  the  eccentric  will  then  be  on 
one  "  dead  center."  From  the  points  J  and  L  scribe  the  arcs  0  P  and 
Q  R,  ending  at  the  points  0  and  Q  on  the  edge  of  the  strap.  From  the 
points  0  and  Q  scribe  arcs  intersecting  at  the  point  8  on  the  edge  of  the 
strap.  With  the  chisel  make  a  mark  on  the  strap  at  8.  Bring  the  eccen- 
tric around  so  that  the  point  F  corresponds  with  the  point  8,  and  the 
eccentric  will  be  on  the  opposite  end  of  the  travel. 

Now  assume  an  engine  equipped  with  the  Meyer  cut-off,  substantially 
as  in  the  illustrations,  i.e.,  a  single  main  valve  and  single  cut-off,  each 


driven  by  one  eccentric.  Also  assume  that  the  builders  have  made  all 
proportions,  lap,  width  of  ports,  and  bridges  correct.  Take  out  the  cut-off 
valve  and  start  to  adjust  the  action  of  the  main  valve,  bearing  in  mind  it 
should  be  set  practically  the  same  as  any  D  slide  valve. 


THE  RIDING  CUT-OFF   VALVE 


49 


Fig.  53  shows  a  steam  chest  with  the  valves  removed.  Take  a  scale 
and  scriber  and  mark  lines  from  the  lower  end  of  the  ports  A  and  C  on 
the  valve  seat  down  to  the  bottom  of  the  valve  chest,  and  with  an  adjust- 
able square  resting  on  the  surface  of  the  valve-chest  flange  carry  out  these 
lines  to  the  points,  a,  6,  d,  and  e  on  the  valve-chest  flange.  Then  bisect 
the  distance  between  the  inner  edges  of  the  steam  ports,  get  a  center  line 


FIG.  53. 


through  the  middle  of  the  exhaust  port  B  and  carry  it  out  in  the  same 
way  to  the  point  c  on  the  steam-chest  flange. 

In  Fig.  54  is  shown  the  main  valve  in  position,  with  the  center  line 
A  corresponding  with  the  center  line  c  on  the  steam-chest  flange.  This 
shows  the  valve  on  the  center  of  travel. 

With  the  main  valve  in  position  and  connected  up,  proceed  as  shown 
in  Figs.  51  and  52,  and  place  the  eccentric  on  the  "  dead  center  "  nearest 


50 


VALVE  SETTING 


the  engine  cylinder.  With  a  scriber  mark  downward  on  the  edge  of  the 
valve  farthest  from  the  eccentric,  which  will  result  in  the  line  ra  on  the 
valve  seat  (Fig.  53).  Move  the  eccentric  to  a  point  opposite  the  center 
and  scribe  downward  along  the  same  edge  of  the  valve1,  which  will  give 
line  k  on  the  valve  seat.  With  the  dividers  or  scale  locate  and  mark  the 
line  I  on  the  valve  seat,  half  way  between  the  lines  fc  and  ra.  Then  turn 


FIG.  54. 


the  eccentric  around  until  the  same  edge  of  the  valve  comes  to  the  line  I 
The  center  line  A  on  the  valve  should  now  correspond  with  the  line  c 
on  the  steam-chest  flange,  as  shown  in  Fig.  54. 

With  the  valve  in  midposition,  reach  through  its  ports  a  and  I,  Fin. 
54,  with  a  scriber  and  mark  along  its  steam  edges  on  the  valve  faces  UK- 
lines  i  and  ;  (Fig.  53). 

Upon  removing  the  valve  again  it  can  be  seen  what  the  lap  is,  and 


THE   RIDING  CUT-OFF   VALVE  51 

whether  it  is  even,  by  measuring  from  the  line  t  to  the  nearest  edge  of 
the  port  A,  and  from  the  line  j  to  the  nearest  edge  of  the  port  (7. 

When  it  is  impossible  to  see  the  valve  seat  with  the  main  valve  in 
position,  so  as  to  scribe  the  lines  Tc,  I,  and  m  (Fig.  53)  on  the  valve  seat, 
proceed  as  follows : 

After  marking  the  port  lines  and  center  on  the  valve-chest  edge,  as 
shown  in  Fig.  53,  replace  the  valve  and,  placing  the  eccentric  on  the  center 
nearest  the  cylinder,  with  the  scriber  mark  a  line  /  on  the  valve  stem 
where  it  leaves  the  stuffing-box  gland.  Placing  the  eccentric  on  the  oppo- 
site center,  mark  a  line  h  on  the  valve  stem  at  the  same  point  at  the  edge 
of  the  gland.  Find  and  mark  the  line  g  half  way  between  f  and  h  and 
turn  the  eccentric  so  that  the  line  g  is  just  entering  the  gland.  The  valve 
should  be  on  the  center  of  its  travel  and  its  center  line  A,  Fig.  54,  should 
correspond  with  the  line  c.  If  this  latter  process  is  followed,  care  should 
be  taken  to  have  the  stuffing-box  gland  pulled  up  so  that  it  will  not  move 
in  or  out  with  any  movement  of  the  stem. 

In  Fig.  54  the  marks  are  shown  on  the  cut-off  valve  stem,  as  it  is 
easiest  seen,  but  the  same  application  applies  to  both  stems. 

Now  place  the  engine  on  "  dead  center  "  and  pull  the  eccentric  around 
until  the  lead  is  given  and  then  fix  the  eccentric  in  position.  Pull  the  en- 
gine around  to  opposite  "  dead  center/'  and  observe  the  lead  on  that  end. 
Make  the  lead  the  same  on  each  end,  or  make  the  usual  allowances  for 
the  crank  end  of  a  horizontal  engine  or  the  bottom  end  of  a  vertical  en- 
gine, as  determined  by  the  builder.  Place  the  cut-off  valve  in  position 
connected  up  to  valve  stem.  Use  the  same  precautions  on  the  cut-off 
eccentric  as  with  the  main  eccentric  to  get  (f  dead  center/' 

Then  when  the  main  valve  is  in  midposition  place  the  cut-off  valve 
in  the  same  position,  and  observe  if  the  cut-off  edges  are  the  same  dis- 
tance from  the  steam  edges  of  the  main  valve.  If  they  are,  set  the  en- 
gine at  one  half  its  stroke.  To  do  this,  divide  the  distance  H  and  R 
on  the  guide  </,  Fig.  50  (which  distances  denote  the  end  of  the  stroke), 
so  as  to  get  point  T.  Let  the  mark  A  correspond  to  T.  Now  pull  the 
cut-off  eccentric  around  until  the  cut-off  valve  edge  is  line  and  line  with 
the  cut-off  edge  of  the  main  valve.  Set  the  cut-off  eccentric  and  pull 
the  engine  over  to  one-half  stroke,  going  in  the  opposite  direction.  Ob- 
serve if  the  cut-off  is  the  same.  If  not,  then  the  eccentric  must  be  set 
ahead  or  back  to  even  it  up. 

With  both  eccentrics  set  and  secured  in  place,  turn  the  engine  around 
and  observe  that  there  is  no  reopening  of  the  cut-off  valve  after  it  has 
cut  off  and  before  the  main  valve  has  cut  off.  Bear  in  mind  the  points 
brought  out  as  to  position  of  the  eccentrics  and  lap  of  the  valves  in  refer- 
ence to  cutting  off  before  or  after  one-half  stroke. 

Where  cut-off  valves  are  operated  by  automatic  governors  all  the  rules 


52  VALVE   SETTING 

here  mentioned  are  to  be  observed  when  the  governor  weights  are  resting 
at  the  inner  position  of  their  travel  with  everything  connected  up.  After 
the  valve  setting  is  all  done,  the  governor  spring  or  springs  should  be 
disconnected  and  the  governor  parts  blocked  out  to  the  other  extreme 
position.  Then  while  the  engine  is  turned  a  complete  revolution,  it  should 
be  observed  that  the  cut-off  valve  covers  the  main  valve  ports  at  all  points 
of  the  revolution.  For  finer  adjustment  of  the  valves  recourse  must  be  had 
to  the  indicator. 


THE    CORLISS    STEAM    ENGINES* 

To  equalize  the  clearance  at  both  ends  of  the  steam  cylinder,  place 
the  crank  pin  upon  its  forward  dead  center,  loosen  the  piston-rod  nut,  and 
screw  the  piston  into  the  crosshead  until  it  is  brought  up  against  the 
front  head  of  the  cylinder;  after  which  screw  up  the  nut  until  it  touches 
the  crosshead  hub  without  jamming.  Now  place  the  crank  pin  upon  its 
opposite  dead  center  and  back  out  the  piston  rod  until  the  piston  is  forced 
against  the  back  head,  being  careful  not  to  disturb  the  position  of  the 
nut  upon  the  rod.  The  distance  between  the  face  of  the  nut  and  cross- 


FIG.  55. 

head  hub  represents  the  total  clearance  of  the  cylinder,  which  should  be 
adjusted  by  screwing  the  piston  rod  into  the  crosshead  half  of  the  amount 
of  total  clearance  and  tightening  and  the  nut. 

This  method  is  sufficiently  accurate  for  all  practical  purposes  if  care 
is  exercised  not  to  disturb  the  position  of  the  nut  upon  the  rod.  A  better 
way  if  time  permits  is  to  mark  in  some  convenient  position  upon  the 
crosshead  guide  the  stroke  of  the  engine,  obtained  by  placing  the  crank 
pin  upon  its  opposite  dead  centers,  scribing  these  lines  coincident  to  the 
same  edge  of  the  crosshead  shoe.  Remove  the  connecting  rod,  and  force 
the  piston  alternately  against  the  back  and  front  heads  of  the  cylinder, 

*  Contributed  to  Power,  by  John  L.  Flock. 
53 


54  VALVE  SETTING 

scribing  both  positions  upon  the  guide,  using  the  same  edge  of  the  cross- 
head  shoe  as  before.  The  distance  between  these  two  marks  will  represent 
the  stroke  of  the  engine  plus  the  total  clearance;  subtracting  from  this 
the  stroke  of  the  engine  will  give  the  total  clearance  of  the  cylinder. 

Now  place  the  connecting  rod  in  position  with  the  crank  pin  upon  the 
forward  dead  center  and  the  piston  against  the  front  head.  Screw  up  the 
piston-rod  nut  until  it  touches  the  crosshead  hub  without  jamming,  and 
equalize  the  clearance  by  backing  the  piston  rod  out  of  the  crosshead,  a 
distance  equal  to  half  of  the  total  amount  of  clearance,  measuring  be- 
tween the  face  of  the  nut  and  end  of  the  crosshead  hub,  as  before,  and 
set  up  the  nut. 

After  the  clearance  has  been  ascertained  a  good  plan  is  to  place  a 
center  punch  mark  upon  the  piston  rod  and  crosshead  hub  parallel  to  the 
axis  of  the  cylinder,  and  make  a  gauge  of  J-in.  round  steel,  the  distance 
between  the  points  of  which  equals  that  of  the  center  punch  marks.  This 
gauge  will  be  found  of  the  greatest  convenience  should  it  at  any  time  be 
necessary  to  dismantle  the  engine.  All  that  is  required  to  readjust  the 
clearance  on  assembling  the  engine  is  to  screw  the  piston  rod  into  the 
crosshead,  until  the  center  punch  marks  coincide  with  the  points  of  the 
gauge. 

To  set  the  valves  of  horizontal  Corliss  steam  engines,  proceed  as  fol- 
lows: Take  off  the  back  bonnets  and  remove  the  valves.  With  a  sharp 
chisel  mark  upon  their  back  end  a  line,  touching  the  circumference  of 
the  valves,  coincident  to  the  steam  edges  of  the  valves,  and  also  place 
marks  in  some  convenient  position  on  the  valve  housings  representing  the 
edges  and  width  of  the  steam  ports,  and  replace  the  valves.  Place  the 
swing  plate  and  rocker  arm  in  a  vertical  position,  with  crank  pin  on  its 
dead  center  toward  steam  cylinder,  and  mark  the  swing-plate  hub,  pro- 
longing the  line  upon  the  swing-plate  bracket.  Loosen  the  eccentric  and 
rotate  it,  adjusting  the  eccentric  rod  so  that  the  line  upon  the  swing- 
plate  hub  vibrates  equally  distant  each  side  of  the  line  upon  the  swing- 
plate  bracket,  after  which  secure  the  swing  plate  in  its  vertical  position 
by  inserting  several  thicknesses  of  emery  cloth  under  the  washer  of  the 
swing-plate  stud  and  tightening  the  nut.  Give  the  steam  and  exhaust 
valves  their  required  lap,  using  for  this  purpose  a  pair  of  dividers  and 
measuring  from  the  mark  representing  the  cut-off  edge  of  the  port  and 
steam  edge  of  the  valve  on  the  circumference.  After  the  steam  and  ex- 
haust rods  have  been  secured  for  equal  lap  at  both  ends  of  the  steam 
cylinders,  release  the  swing  plate  and  advance  the  eccentric  forward  upon 
the  shaft,  until  the  line  representing  the  edge  of  the  left-hand  steam  valve 
has  traveled  beyond  the  incision  representing  the  cut-off  edge  of  the  port 
indicating  lead,  and  secure  the  eccentric  to  the  shaft.  The  engine  should 
now  be  rotated  and  the  marks  upon  all  four  valves  carefully  gone  over, 


THE  CORLISS  STEAM  ENGINES  55 

to  ascertain  whether  the  lead  is  equal  at  both  ends  and  the  valves  have 
sufficient  overtravel  to  prevent  wire  drawing  at  early  cut-off.  Half-inch 
overtravel  with  -fa  in.  lead  will  be  found  adequate  for  the  majority  of 
engines;  the  steam  lap  should  be  from  i  to  f  in.,  with  exhaust  lap  rang- 
ing from  ^  to  -fa  in.,  depending  upon  the  size  of  the  engine  and  the 
amount  of  compression  required.  The  lead  of  the  exhaust  valves  should 
always  be  in  excess  of  that  of  the  live  steam  valves,  so  that  just  on  the 
point  of  opening  the  live  steam  valves  still  have  lap  to  prevent  the  blowing 
through  of  steam.  This  completes  the  setting  of  the  eccentric,  rocker  arm, 
swing  plate,  and  steam  and  exhaust  valves  as  far  as  can  be  done  without 
the  use  of  an  indicator. 

Adjust  the  coupling  rod  between  the  governor  weight  bar  lever  A  so 
that  it  oscillates  equally  out  of  its  horizontal  position  when  the  governor 
balls  are  brought  into  its  highest  and  lowest  position. 

When  the  steam  engine  is  to  be  started,  the  steam,  cylinder  must  be 
able  to  receive  the  full  steam  pressure,  and  the  steam  valves  must  not  be 
tripped.  To  enable  this  to  be  done,  governors  of  Corliss  engines  are  sup- 
plied with  a  loose  collar  D  having  a  slot  E  fitted  to  the  governor  banjo, 
or  a  loose  pin  which  is  fitted  to  a  series  of  holes  and  performs  the  same 
functions  as  the  collar. 

When  the  governor  balls  have  attained  their  normal  position,  the  collar 
should  be  set  so  as  to  allow  the  lifting  sleeve  F  to  sink  below  the  upper 
edge  of  the  collar  into  the  slot  E.  If  a  pin  is  used,  it  should  be  removed 
for  the  same  purpose.  The  reason  for  this  is  obvious,  for  should  the  gov- 
ernor belt  break  while  the  governor  is  in  this  position,  the  trip  rods  B 
and  C  will  place  the  safety  toes  G  in  such  a  position  as  to  permanently 
unhook  the  live  steam  valves,  and  the  engine  will  stop.  When  starting, 
the  collar  or  pin  is  placed  so  that  the  safety  toes  are  out  of  action. 

To  adjust  the  trip  cams  H  and  safety  toes  G,  place  the  governor  lift- 
ing sleeve  upon  the  top  of  the  collar  D  as  in  the  position  for  starting 
the  engine,  rotate  the  crank  shaft  so  that  the  eccentric  is  in  its  extreme 
forward  position,  as  shown  in  the  drawing.  The  correctness  of  this  posi- 
tion is  assured  by  referring  to  the  marks  upon  the  swing-plate  hub  and 
bracket.  The  mark  denoting  the  vertical  position  of  the  swing  plate 
should  now  coincide  with  that  upon  the  bracket  representing  the  forward 
travel  of  the  swing  plate.  Shorten  or  lengthen  the  trip  rod  B,  as  the 
case  may  be,  so  that  the  trip  cam  H  will  just  touch  the  block  upon  the 
latch  hook  without  disengaging  the  hook  from  the  latch  block  upon  the 
steam  lever,  but  will  do  so,  allowing  the  valve  to  cut  off,  when  a  piece  of 
iron  or  wood,  J  in.  thick,  is  inserted  between  the  top  edge  of  collar  D 
and  governor  lifting  sleeve  F. 

Set  the  safety  toe  G  in  such  a  position  as  will  fully  and  securely  un- 
hook the  live  steam  valve  when  the  collar  D  is  turned  for  regular  running, 


TABLE   SHOWING   PRINCIPAL  DIMENSIONS  AND  HORSE    POWER   OF  CORLISS  ENGINES 

WITH  DIFFERENT  STEAM  PRESSURES  AND  POINTS  OF  CUT-OFF 


J 

•8 

1 

10X20 
10X24 
10X30 

11X20 
11X24 
11X30 

12X24 
12X30 
12X36 

Revolutions  per  Minute 

K 

lf 

1 

Boiler  Pressure 
90  Pounds 

Boilar  Pres3ure 
100  Pounds 

Boiler  Pressure 
125  Pounds  . 

Band  -Wheel 

Weight  of  Engine 
and  Fly-Wheel 
Complete 

! 

• 

I 

Exhaust  Lap 

Trial  Compression* 

1  Steam  Diam.  ^ 
1  .=• 

Exhaust  * 
Diam.  1 

I. 

1 

Weight 

Point  of  Cut-off 

Point  of  Cut-off 

Point  of  Cut-off 

1-5 

1-4 

1-3 

1-5 

1-4 

1-3 

1-5 

1-4 

1-3 

ft 

In. 

Pounds 

Pounds 

Inches 

In. 

In. 

120 
120 
100 

400 
480 
500 

38 
45 
47 

45 
54 
57 

w 

66 
69 

43 
51 
54 

53 
61 
64 

.62 
74 

78 

56 
66 

70 

63 
75 

79 

77 
92 
96 

7 
8 
8 

13 
13 
13 

4,500 
5,000 
5,400 

10,500 
12,270 
13,250 

| 

t4 

£ 

y 

a 

i1 

3 

3 
4 

4 

120 
120 
100 

400 
480 
500 

46 
55 
57 

52 
67 
69 

63 
82 
84 

52 
62 
65 

62 
74 

77 

75 
89 
94 

68 
71 
84 

76 
83 
95 

93 
101 
116 

8 
8 
8 

13 
13 
13 

6,000 
7,000 
7,800 

14,000 
14,600 
18,000 

« 

it 

• 

- 

a 

11 

3 
3 
3 

4 

4 
4 

120 
90 
85 

480 
4£0 
480 

65 
62 
70 

78 
74 
84 

93 
100 
114 
128 

132 
144 
159 
176 

~\fj 
185 
202 
222 

228 
240 
263 
297 

310 
290 
304 
318 
359 

95 
90 
102 

74 

I 

87 
183 
94 

106 
101 
114 

96 
89 
101 

107 
102 
116 

131 
144 
152 

9 
9 
10 

13 
13 
15 

9,100 
10,000 
10,300 

19,300 
21,100 
22,500 

a 
J 

u 

2a 

3 
3 

3* 

4 
5 
5 

14X28 
14X32 
14X36 
14X42 

95 
90 
85 
82 

443 
479 
510 
574 

78 
85 
95 
107 

ito 

120 
133 
145 

114 
.122 
139 
156 

90 
97 
107 
120 

105 
114 
128 
144 

128 
138 
156 
175 

112 
120 
137 
154 

130 
140 
158 
178 

156 
170 
193 
217 

10 
10 
10 
11 

15 
15 
19 
19 

10,500 
10,800 
11,000 
11,400 

22,800 
26,500 
28,500 
29,100 

« 
i 

£ 

- 

2i 

2i 

3 

CnCnCnCn  j  »*»•  »&•  •*>•  *>  1  CO  W  CO  CO 

1  I  '  '*' 

5 
5 
5 
5 

16X32 
16X36 
16X42 
16X48 

90 
82 
78 
75 

80 
80 
78 
75 

479 
492 
546 
600 

480 
533. 
546 
600 

161 
175 
194 
215 

216 
225 
246 
271 

278 
292 
321 
362 

126 
135 
150 
165 

149 
162 
179 
199 

182 
197 
218 
242 

158 
173 
192 
215 

184 
200 
221 
245 

246 
258 
281 
308 

224 
244 
269 
299 

12 
1.2 
12 
12 

12 
12 
14 
16 

21 
21 
23 
25 

12,000 
12,300 
12,600 
13,000 

29,100 
29,400 
34,800 
34,840 

u 
u 

u 

2 
2i 
2* 

6 
6 
6 
6 

18X36 
18X40 
18X42 
18X48 

148 
156 
168 
185 

166 
179 
189 
208 

199 
210 
227 
249 

242 
256 
277 
504 

314 

329 
361 
407 

214 
222 
244 
268 

300 
312 
321 
376 

25 
25 
25 
25 

25 
31 
31 
33 

31 
33 
37 
37 
31 

14,000 
14,600 
15,000 
16,000 

34,900 
.  36,000 
37,900 
42,900 

1 

« 

• 

it 
" 

u 
u 

it 

2i 
* 

3 

7 
7 

20X40 
20X42 
20X48 
20X60 

80 
75 
72 
65 

533 
525 
576 
650 

192 
200 
219 
248 

220 
225 
246 
279 

257 
270 
296 
334 

350 
326 
343 
358 
404 

273 
289 
317 
358 

317 
333 
365 
413 

385 
406 
445 
504 

16 
16 
16 
14 

17,000 
18,000 
.20,000 
20,800 

45,500 
48,300 
50,150 
51,000 

a 
u 
u 

u 

2* 

I1 

5 
5 
5 
£ 

7 

7 
7 

7 

22X36 
22X42 
22X44 
22X48 
22X60 

100 
75 
80 
72 
65 

600 
525 
586 
576 
650 

262 
242 
256 
265 

299 

380 
343 
370 
388 
'433 

300 
271 
292 
298 
336 

360 
323 
345 
386 
401 

427 
398 
418 
437 
493 

373 
350 
361 
385 
433 

435 
403 
425 
443 
499 

631 
•491 
518 
540 
609 

16 
14 
14 
1.6 
16 

16 
16 
16 
16 
18 

21,300 
22,000 
23,000 
24,000 
24,500 

51,900 
53,650 
56,600 
60,000 
61,500 

H 

tt 

u 

u 
u 
u 
u 

2J 
2* 
2| 

6 
6 
6 
6 
6. 

0000000000  j  OJOSOOO 

24X36 
24X42 
24X48 
24X52 
24X60 

100 
75 
70 
75 
65 

600 
525 
560 
619 
650 

314 
287 
307 
338 
356 

371 
347 
368 
400 
427 

•455 
423 
448 
490 
520 

420 
392 
414 
450 
481 

512 
478 
505 
650 
'587 

445 
420 
444 
480 
515 

•520 
482 
511 
560 
594 

634 
588 
723 
683 
724 

37 
40 
40 
40 
40 

25,000 
26,000 
27,000 
26,300 
"28,000 

62,500 
64,000 
81,300 
84,500 
90,000 

A 

u 

ti 
u 

u 

u 

2J 
2| 

2J 

u 

7 
7 
7 
7 
7 

26X36 
26X48 
26X52 
26X54 
26X56 
26X60 

100 
70 
75 
70 
70 
65 

600 
560 
649 
630 
522 
650 

366 
360 
395 
404 
398 
418 

433 
432 
469 
455 
472 
£02 

530 
627 
572 
555 
575 
612 

420 
405 
454 
455 
457 
470 

490 
486 
530 
546 
633 
564 

698 
593 
646 
661 
650 
688 

520 
521 
560 
592 
563 
602 

6Q7 
600 
655 
672 
659 
693 

740 
732 
799 
820 
804 
845 

18 
16 
16 
16 
18 
18 

40 
40 
40 
40 
40 
40 

29,000 
32,000 
30,000 
31,500 
36,000 
34,000 

90,500 
92,000 
92,000 
92,500 
93,600 
94,000 

a 
u 

u 

A 

u 

A 

V 
k 

tt 

7 
7 
7 
7 
7 

10 
10 
10 
10 
10 
10 

'Distance  of  piston  from  end  of  stroke  in  inches. 


TABLE    SHOWING   PRINCIPAL  DIMENSIONS   AND   HORSE  POWE~R   OF  CORLISS  ENGINES 
WITH  DIFFERENT  STEAM  PRESSURES  AND  POINTS  OF  CUT-OFF— Continued 


1 

i 

28X36 
28X48 
28X52 
28X54 
28X56 
28X60 

"3 
•3 

100 
68 
75 
70 
70 
65 

i. 

600 
544 
649 
630 
522 
650 

Boiler  Pressure 
90  Pounds 

Boiler  Pressure 
100  Pounds  • 

Boiler  Pressure 
125  Pounds 

Band  Wheel 

ll. 

JP 

Steam  Lap 

Steam  Lead 

Exhaust  Lap 

Trial  Compression*  1 

Pit 

Q 
00 

Exhaust  1  *  I 
Diam.  1  | 

i 

l 

Weight 

Point  of  Cut-off 

Point  of  Cut-off 

Point  of  Cut-off 

1-5 

488 
406 
460 
469 
463 
485 

•1-4 

678 
487 
545 
563 

548 
582 

1-3 

1-5 

1-4 

1-3 

1-5 

1-4 

1-3 

Ft. 

In. 

Pounds 

Pounds 

Inches 

In. 

In. 

8'27 
594 
'665 
696 
669 
710 

560 
457 
525 
528 
528 
545 

655 
548 
616 
624 
620 
654 

809 
668 
751 
761 
755 
804 

693 
588 
652 
686 
657 
700 

810 
677 
760 
768 
765 
807 

988 
826 
927 
937 
933 
968 

18 
18 
18 
18 
18 
20 

40 
40 
40 
40 
40 
40 

35,000 
34,000 
35,000 
37,000 
37,500 
36,QOO 

94,800 
95,000 
94,500 
95,000 
94,500 
137^000 

i6 

$ 

a 

# 
a 
it 
a 

u 

31 

8 
8 
8 
8 
8 
8 

10 

10 
10 
10 
10 
10 

30X36 
30X48 
30X52 
30X54 
30X56 
30X60 
30X72 

100 
68 
'75 
70 
70 
62 
55 

600 
544 
700 
630 
653 
620' 
660 

488 
466 
528 
538 
535 
531 
565 

678 
559 
626 
646 
J533 
637 
678 

700 
682 
765 
788 
774 
777 
827 

560 
542 
599 
607 
605 
597 
635 

655 
629 
710 

727 

718 

'717 

795 
773 
862 
894 
872 
882 
937 

693 
674 
752 
789 
760 
770 
817 

810 
776 
876 
970 
886 
886 
942 

970 
931 
1057 
1164 
1070 
1063 
1130 

20 
20 
20 
20 
22 
22 
22 

40 
40 
40 
40 
40 
40 
40 

37,600 
38,000 
38^400 
39,000 
38,000 
40,000 
41,000 

138,000 
140,000 
140,000 
141,500 
144,500 
149,000 

u 

u 

u 

A 

4( 

3J 

8 
8 
8 
8 
8 
8 
8 

0000000  1 

32X48 
32X52 
32X56 
32X60 
32X72 

75 
75 
70 
62 
55 

600 
700 
653 
620 
660 

555 
600 
608 
604 
643 

658 
712 
720 
725 
772 

802 
870 
880 
885 
926 

628 
680 
687 
680 
723 

745 
807 
814 
816 
868 

905 
980 
990 
996 
1058 

790 
853 
862 
975 
931 

920 
996 
1005 
1007 
1073 

1110 
1195 
1216 
1208 
1288 

22 
22 
22 
22 
22 

54 
54 
40 
40 
54 

42,000 
43,200 
44,000 
45,000 
49,000 

«. 

l<! 

\ 

a 
u 
a 

4  ' 

10 
10 
10 
10 
10 

12 
12 
12 
12 
12 



34X48 
34X60 
34X72 

65 
62 
55 

520 
620 
660 

572 
682 
726 

686 
871 

823 
981 
1Q45 

644 
767 
817 

772 
920 
980 

942 
1122 
1195 

828 
987 
1051 

954 
1137 
1211 

1145 
1364 
1453 

22 
24 
22 

i$52 
24 
25 
25 

54 
60 
54 

53,500 
50,000 
53.000 

a' 

u 

a 

u 
u 

31 
3* 

10 
10 
10 

12 
12 
12 

36X48 
36X60 
36X72 
38X60 

62 
62 
55 
60 

496 
620 
660 
600 

611 
665 
814 
824 

749 
918 
•977 
f007 

899 
1101 
1172 
1208 

688 
86,0 
916 
9?8 

825 
1032 
1099 
1113 

1006 
1259 
1318 
1336 

886 
1107 
1178 
1183 

1020 
1275 
1357 
1363 

1224 
1530 
1628 
1636 

54 

"60 
60 
60 

55,000 
59,000 
62,000 
68,000 

I 

| 

U 
a 
a 

\ 

4 
3} 

12 
12 

12 
14 

14 
14 
14 
16 

40X48 
40X60 
40X72 
40X84 

70 
62 
55 
50 

560 
620 
660 
720 

852 
944 
1005 
1066 

1044 
1133 
1206 
1305 

1253 
136.0 
1447 
1566 

959 
1062 
1130 
1199 

1150 
1274 
1356 
1439 

1380 
1529 
1627 
1727 

1523 
1686 
1795 

1235 
1367 
1455 
1543 

1422 
1574 
1676 
1777 

1706 
1889 
2011 
2132 

25 
25 
26 
26 

60 
60 
60 
60 

73,000 
78,000 
84,000 
90,000 

it 

A 

u 

i 

3 

9 

(i 

; 

42X48 
42X60 
42X72 

44X48 
44X60 
44X72 

70 
62 
55 

70 
62 
55 

560 
620 
660 

940 
1041 
1108 

1151 
1249 
1330 

1234 
1370 
1459 

1381 
1499 
1596 

1481 
1644 
1751 

1057 
1171 
1246 

1269 
1405 
1496 

1393 
1542 
1642 

1361 
1507 
1604 

1567 
1736 
1847 

1721 
1905 
2028 

1880 
2083 
2216 

26 
26 
27 

60 
60 

92,000 
94,000 
96,000 

\ 

A 

"t 

it 

4 

3* 

J 

\ 

:::::.: 

560 
620 
66C 

1031 
1142 
1216 

1039 
1285 
1368 

1672 
1850 
1970 

1494 
1653 
1761 

2065 
2286 
2434 

27 

28 
28 

•  •  • 

98,000 
100,000 
102,000 



I 

A 

16 

18 

46X60 
46X72 

62 
55 

62( 
660 

1249 
1329 

1499 
1595 

1799 
1914 

1405 
1495 

1686 
1794 

2023 
2153 

1807 
1924 

2082 
2217 

2498 
2660 

29 
29 

104,000 
106,000 

" 

u 

3* 

41 

a 

a 

48X60 
48X72 

62 

55 

620 
660 

1360 
1447 

1632 
1737 

1958  1530 
2084  1628 

1835 
1954 

2202 
2345 

1969 
2096 

2268 
2414 

2721 
2897 

30 
30 

108,000 
110,000 

u 

.u 

4* 

u 
u 

« 



'Distance  of  piston  from,  end  of  stroke  in  inohee. 


58  VALVE   SETTING 

but  will  not  do  so  when  set  for  starting.  Reverse  the  extreme  position 
of  the  eccentric  and  adjust  the  trip  rod  C  as  described  for  B. 

Set  the  length  of  the  dashpot  rods  so  that  when  the  swing  plate  is  in 
its  extreme  position  to  the  right,  the  cut-off  toe  of  valve  K  is  in  the  mid- 
dle of  both  stops  provided  on  its  disengaging  lever.  The  first  stop  is  that 
which  lifts  the  dashpot  piston;  the  second  stop  is  the  one  which  will  bring 
the  dashpot  piston  to  its  lowest  position  in  case  it  has  not  assumed  it 
of  its  own  accord,  and  when  the  swing  plate  is  in  its  extreme  position  to 
the  right,  the  cut-off  toe  of  the  valve  L  is  in  the  middle  of  both  stops 
on  its  respective  disengaging  lever.  The  dashpot  should  be  well  lubri- 
cated, being  careful  that  the  quantity  supplied  is  not  sufficient  to  choke 
the  air  passages,  for  by  so  doing  the  dashpot  is  liable  to  be  broken  when 
the  dashpot  plunger  drops.  The  air-regulating  valve  should  be  adjusted 
so  that  the  plunger  will  drop  sufficiently  to  allow  the  latch  hook  to  engage 
the  cut-off  toe  upon  the  steam  lever  without  striking  the  bottom  of  the 
dashpot.  Should  the  plunger  descend  too  quickly  the  valve  should  be 
regulated  until  the  required  speed  is  attained.  When  carrying  steam  full 
stroke  (not  cutting  off),  the  regulating  valves  should  be  opened  to  relieve 
the  steam  valves  from  the  additional  strain  transmitted  by  the  dash  pots. 
If  the  governor  is  equipped  with  an  oil  dashpot,  it  should  be  kept  full 
of  a  not  too  heavy  oil.  If  this  is  neglected,  the  governor  will  have  an 
irregular  motion  in  jerks  corresponding  to  the  height  of  the  dashpot  not 
occupied  by  the  oil.  The  tension  of  the  governor  belt  should  be  sufficient 
to  prevent  any  tendency  to  slip  if  smooth,  regular  running  is  to  be 
assured. 

When  the  various  parts  of  a  Corliss  valve  gear  are  in  their  proper 
adjustment,  the  reach  rod  should  be  of  such  a  length  that  both  the  rocker 

arm  and  the  wrist  plate  will  be 
plumb  when  the  eccentric  occupies 
the  central  position,  as  in  Fig.  56, 
and  marks  A  B  should  be  made  on 
the  hub  and  wrist-plate  stud  at  this 
central  position,  as  shown  in  Fig. 
57.  The  eccentric  should  then  be 
FIG.  ^•-PL™BCIKNEGRWARR«T  PLATE  AND  turned  to  one  of  its  extreme  posi- 

tions.    A  temporary  mark  should  be 

made  here  lightly  as  at  D,  Fig.  58.  The  eccentric  should  then  be  turned 
to  the  opposite  position  and  another  mark  made  at  C.  The  distance  from 
B  to  C  should  equal  the  distance  from  B  to  D.  If  thnv  is  any  discrepancy 
the  reach  rod  should  be  lengthened  or  shortened  until  the  distance  which 
the  wrist  plate  travels  on  cadi  side  of  the  mark  />'  is  the  same,  \vhni  tin- 
rod  will  be  of  the  proper  length. 

Disconnect  rod  and  place  the  wrist  plate  in  its  central  position.     With 


THE   CORLISS   STEAM    ENGINES 


59 


the  wrist  plate  in  this  position  and  both  steam  valves  hooked  on,  the 
valves  should  have  the  proper  lap.  This  may  be  ascertained  by  removing 
the  steam  bonnets  and  inspecting  the  marks  on  the  valves  and  seat  made 


FIG.    57. —  CENTRAL   MARKS    ON 
HUB    OF   WRIST    PLATE. 


FIG.    58.  —  WRIST  PLATE    IN 
EXTREME    POSITION. 


by  the  builders,  as  shown  in  Fig.  59,  where  F  is  the  working  edge  of  the 
valve,  E  is  the  edge  of  the  steam  port  and  the  distance  E  D  is  the  lap 
of  the  valve.  The  proper  lap  to  give  the  valves  can  be  found  in  the 
accompanying  table,  and  the  radial  arms  should  be  lengthened  or  short- 
ened by  means  of  the  left-  and  right-hand  thread  connections  until  the 
lap  is  equalized  and  of  the  right  amount. 

Then  turn  the  wrist  plate  to  the  extreme  travel  on  the  head  and  ad- 


FIG.    59. —  SHOWING   MARKS 
ON    VALVE   SEAT. 


FIG.    60.  —  ADJUSTING   CLEARANCE 
AT    CATCH    BLOCK. 


just  the  length  of  the  dashpot  rod  so  there  will  be  an  equal  clearance 
around  the  catch  block,  as  shown  in  Fig.  60.  Turn  the  wrist  plate  to 
the  other  extreme  and  adjust  the  other  dashpot  rod  in  the  same  manner. 


60  VALVE   SETTING 

Next  with  the  governor  in  its  lowest  running  position  resting  on  the 
collar  or  pin  provided  for  the  purpose,  turn  the  wrist  plate  so  as  to  pick 
up  the  head-end  steam  valve  and  then  turn  it  over  until  it  nearly  reaches 
the  mark  corresponding  to  its  opposite  position,  and  adjust  the  governor 
rod  for  the  head-end  valve  so  that  the  trip  block  E,  Fig.  60,  just  engages 
the  inner  member  of  the  hook  K,  making  sure  that  the  valve  will  be  re- 
leased when  the  wrist  plate  reaches  its  extreme  position.  The  same 
adjustment  should  now  be  made  at  the  crank  end  of  the  cylinder.  The 
governor  should  then  be  blocked  up  to  its  highest  point  of  travel,  when  the 
trip  blocks  should  be  in  such  a  position  that  neither  steam  valve  can  be 
lifted  by  the  hook. 

Next  put  the  governor  down  to  its  lowest  running  position  and  turn 
the  engine  to  the  dead  center  nearest  the  cylinder.  Hook  the  reach  rod 
on  the  wrist  plate  and  turn  the  eccentric  around  in  the  direction  the 
engine  is  to  run  until  the  hook  has  engaged  the  head-end  steam  valve 
and  raised  it  sufficiently  to  open  the  port  to  the  amount  of  the  lead  as 
shown  in  the  table.  Fix  the  eccentric  at  this  point,  then  turn  the  engine 
over  in  the  direction  it  is  to  run  until  the  crosshead  is  at  a  point  deter- 
mined from  the  column  of  trial  compressions  given  in  the  table,  and  which 
varies  from  1-f  to  4  ins.,  according  to  the  size  of  the  engine,  and  examine 
the  crank  and  exhaust  valve.  The  line  indicating  the  edge  of  the  port 
and  edge  of  the  valve  should  exactly  coincide.  If  they  do  not,  adjust 
the  length  of  the  exhaust  valve  rod  as  the  case  requires  until  the  marks 
are  together. 

Continue  turning  the  engine  until  the  crank  end  dead  center  is  reached, 
making  sure  that  the  head-end  steam  valve  has  been  released,  and  see  if 
the  crank  and  valve  has  been  opened  to  the  amount  of  the  lead.  If  not. 
make  any  required  adjustments  in  the  length  of  the  radial  area  operating 
the  crank  and  steam  valve.  Continuing  turning  the  engine  until  the  cross- 
head  is  within  the  same  distance  from  the  end  of  the  return  stroke  as  in 
the  first  instance,  corresponding  to  the  amount  of  trial  compression,  and 
adjust  the  position  of  the  head  and  exhaust  valve  so  that  the  lines  will 
coincide,  as  was  done  at  the  opposite  end  of  the  cylinder.  Make  sure  that 
the  crank-end  steam  valve  is  released  by  the  time  this  stroke  is  completed, 
and  the  valves  will  be  properly  set,  but  should,  of  course,  be  verified  by 
the  indicator.  This  method  applies  to  a  single  eccentric  engine,  but  the 
same  process  can  be  used  in  the  case  of  the  steam  valves  on  double  eccen- 
tric engines  except  that  when  the  wrist  plate  is  in  its  central  position 
and  both  steam  valves  are  hooked  on,  the  valves  should  give  about  one 
fourth  port  opening  on  each  end  instead  of  lapping,  as  in  the  case  of  a 
single  eccentric  engine,  and  very  little  lap  should  be  allowed  when  the 
dashpots  are  down  to  their  extreme  positions — only  enough,  in  fact,  to 
make  the  valves  steam  tight. 


THE  CORLISS   STEAM  ENGINES  61 

Centralization  of  the  valve  gear  is  accomplished  in  the  same  manner 
as  for  single  eccentric  engines,  but  the  steam  and  exhaust  valves  are,,  of 
course,  set  separately.  When  setting  the  steam  eccentric,  the  style  of 
wrist  plate  operating  the  steam  valves  determines  whether  the  eccentric 
should  be  moved  in  the  same  direction  as  the  crank  or  in  the  opposite 
direction,  when  giving  the  valves  lead.  In  any  case,  this  may  be  deter- 
mined by  an  inspection  of  the  style  of  gear  employed.  In  the  same  man- 
ner, an  inspection  of  the  valve  gear  must  be  made  to  determine  in  whicli 
direction  to  turn  the  eccentric  when  adjusting  the  exhaust  valves  at  the 
point  of  closure  or  compression.  If  the  exhaust  wrist  plate  is  moved  by 
an  attachment  above  its  point  of  support,  as  with  the  steam  valves,  the 
eccentric  must  be  moved  in  the  direction  in  which  the  engine  is  to  run, 
and  the  position  of  the  eccentric  will  be  nearly  that  of  the  steam  eccentric. 
If  the  point  of  attachment  of  the  exhaust  reach  rod  is  below  the  point  of 
support,  the  eccentric  must  be  moved  in  the  opposite  direction  to  that  in 
which  the  engine  is  to  run. 


\  I 

THE    GREENE-WHEELOCK   ENG1XK 

THE  Hill  valve  with  Greene  cut-off  is  on  all  makes  of  the  Greene- 
Wheelock  engine  of  to-day.  In  the  first  years  of  its  maintenance  this 
engine  was  installed  extensively  in  Canada,  England,  France,  and  Ger- 
many, as  well  as  in  this  country,  where  more  than  one  thousand  were  put 
in  service  by  the  original  builders.  Successive  builders  have  improved  the 
type  all  the  while,  steadily  placing  them  in  service,  and  to-day  thousands 
of  these  engines  are  in  use  in  this  and  foreign  countries.  For  this  reason. 
and  because  this  valve  gear  is  interesting  to  operators,  this  chapter  is  writ- 
ten to  bring  out  the  principal  points  to  be  considered  in  the  setting  of  the 
valves. 

Each  cylinder  is  equipped  with  four  valves  of  the  Hill  grid-iron  type, 
two  steam  and  two  exhaust  to  each  cylinder,  each  individual  valve  being 
driven  by  a  separate  eccentric.  The  valves  are  arranged  two  cat -li  in  a 
plug,  there  being  one  steam  and  one  exhaust  in  each  plug,  and  one  plu,u  at 
each  end  of  the  cylinder. 

The  best-known  advantages  of  this  valve  and  gear  are  large  port  open- 
ings with  a  minimum  of  travel,  which  in  connection  with  the  Greene  cui-olT 
on  the  steam  and  the  toggle  motion  on  the  exhaust  valves  gives  the  quickest 
action  at  the  right  time  to  both.  A  minimum  lap  is  also  obtained  witli  tin- 
aid  of  the  gear,  an  added  reason  why  it  is  of  first  importance  to  under- 
stand the  movements  of  the  valve  and  gear  and  to  use  care  in  all  adjust- 
ments. 

The  valve  plugs  contain  the  valve  seats  as  an  integral  part  of  the  plug, 
which  are  in  turn  removable  for  repair,  together  with  the  valves  when  in 
position,  and  to  the  plug  is  attached  the  head  which  holds  the  working 
parts  of  the  valve  mechanism.  The  whole  makes  a  complete  removable 
structure,  separate  from  the  cylinder,  which  can  be  disconnected  from  the 
eccentrics  and  removed  from  the  cylinder  in  a  few  minutes  for  inspection, 
repair,  or  permanent  replacement. 

The  arrangement  of  the  valves  below  the  cylinder  is  the  Wheeloek  sys- 
tem. The  advantages  are  short  ports,  small  clearance,  together  with  a 
means  of  discharge  of  the  water  of  condensation  through  the  exhaust  with- 
out entering  the  cylinder,  and  if  in  extraordinary  cases  water  collect^  in 

62 


64 


VALVE   SETTING 


the  cylinder  it  is  relieved  by  the  raising  of  the  inlet  or  steam  valve  from 
its  seat. 

GENERAL  ARRANGEMENT  OF  VALVE  GEAR 

The  general  arrangement  of  the  valve  gear,  eccentrics,  etc.,  can  he  seen 
by  reference  to  Fig.  61,  which  is  the  high-pressure  side  of  a  cross-com- 
pound engine.  The  eccentric  shaft  A  being  geared  to  the  main  shaft  of 
the  engines  at  a  makes  it  positive  in  action.  The  eccentrics  which  actuate 
the  valves  are  at  5,  C,  D,  and  E.  These  eccentrics  are  secured  to  the  shaft 

by  a  friction  key,  which  is  hidden  by 
a  plate  on  the  side  of  the  eccentric, 


FIG.   62. 


FIG.    63. 


secured  in  place  by  screws.  The  eccentrics  C  and  D  are  the  steam  eccen- 
trics and  B  and  E  the  exhaust.  They  are  attached  to  the  valve  mechanism 
by  their  respective  rods.  The  throttle  of  the  engine  at  F  admits  steam 
to  the  steam  chest  under  the  cylinder  and  equally  to  the  valve  plu^s  Cr 
and  PL 

An  understanding  of  the  valve  plugs  and  their  location  may  be  had  by 
reference  to  Figs.  62,  63,  and  64.  Fig.  62  shows  a  longitudinal  section 
of  the  cylinder  and  the  cross  section  of  the  valve  plug  at  A.  This  view 
gives  the  location  of  the  inlet  (steam)  valve  and  seat  at  a  and  the  outlet 
(exhaust)  valve  and  seat  at  &,  the  steam  chest  B  B  forming  a  jacket  for 
part  of  the  cylinder,  as  well  as  admitting  the  steam  through  the  inlet  a 
into  the  cylinder.  From  the  cylinder  the  steam  passes  out  through  the 
outlet  &  into  the  exhaust  passage  C. 


THE   GREENE-WHEELOCK  ENGINE 


65 


Fig.  63  is  a  cross  section  of  the  cylinder  through  the  clearance  space 
and  a  longitudinal  of  the  valve  plug  in  that  end  of  the  cylinder,  showing 
the  back  of  the  inlet  valve  seat,  with  the  outlet  valve  cut  away. 

Fig.  64  is  a  view  of  the  valve  plug  with  all  the  parts  assembled.  This 
view  shows  the  inlet-  or  steam-valve  side  of  the  plug.  The  inlet  valve  is 
at  a;  the  spring  which  holds  it  to  its  seat  when  not  under  steam  pressure 
is  at  &;  and  c  is  the  pusher  crank  which  actuates  the  valve  by  means 
of  a  cam  at  d,  which  comes  in  contact  with  the  latch  of  the  valve-stem 
head  e.  This  is  fastened  to  the  inlet  valve-stem  by  clamp  bolts.  The 
inlet  valve-stem  screws  into  the  nut  /,  so  that  by  loosening  the  clamp  bolts 


FIG.   64. 


of  the  head  e  and  turning  the  rod,  an  adjustment  of  the  valve  setting  can 
be  made,  as  will  be  shown  later. 

The  inlet  valve  is  opened  by  the  pusher  cam  pushing  it  forward,  but 
is  released  from  this  cam  through  the  means  of  a  trip  cam  on  the  bottom 
of  the  valve-plug  head,  which  is  connected  to  the  governor  rods.  When 
released  by  the  trip  cam,  the  valve  cuts  off  by  means  of  the  steam  pressure 
on  the  valve  stem  controlled  by  a  dashpot  arrangement  in  the  valve-plug 
head,  to  which  the  other  end  of  the  rod  is  attached. 

The  outlet  valve  is  inside  of  the  valve  plug  under  the  strut  g.  The 
position  of  this  valve  in  relation  to  the  inlet  can  be  noted  by  reference 
to  Fig.  62,  where  the  cross  section  of  the  valves  and  seats  is  shown.  The 
outlet  valve  is  actuated  by  the  eccentric  acting  on  the  toggle  joint  h,  con- 
nected between  the  two  pairs  of  links,  from  the  point  i,  where  it  is  fixed, 
and  the  point  /,  where  the  link  is  fastened  to  the  valve-rod  head  k  on  the 
outlet  valve  stem. 


66 


VALVE   SETTING 


POSITION  OF  VALVES  IN  THE  PLUGS 

A  more  thorough  understanding  of  these  valves  may  be  obtained  if  the 
position  of  the  valve  inside  the  plug  (in  relation  to  the  position  of  the 
eccentric  and  other  mechanism)  is  known. 

B 


FIG.    65. 


For  the  sake  of  simplicity,  each  valve,  i.e.,  outlet  and  inlet,  is  shown 
with  its  gear  separate  for  the  moment,  eliminating  one  while  the  other  is 
under  consideration.  The  cross  section  of  the  valve  and  seat  is  not  in 


THE   GREENE-WHEELOCK  ENGINE 


67 


proper  relative4  position,,  but  so  placed  in  these  figures  as  to  best  show  the 
positions  at  given  points  of  the  eccentric  travel. 

Fig.  65  represents  the  inlet  (steam)  valve  and  mechanism  assembled. 
The  scale  is  for  a  size  these  makers  build  for  cylinders  under  16  in.  in 
diameter,  or  their  "  size  A  "  valve.  It  shows  the  valve  lapped  at  the  inner 
end  of  its  travel,  with  the  eccentric  at  the  top  center  of  its  travel. 

Eeferring  to  the  illustration,  then,  A  A  is  the  center  line  of  the  eccen- 
tric shaft,  B  B  is  the  center  line  of  the  eccentric  rod,  C  C  is  the  center  of 


FIG.   66. 


the  pusher  crank  at  the  top  of  its  movement,  D  D  is  the  pusher-crank 
center  at  the  lower  end  of  its  travel,  E  E  is  the  center  line  of  the  pusher- 
crank  shaft,  F  F  is  the  line  of  travel  of  the  pusher-plate  edge,  G  G  is  the 
line  of  travel  of  the  pusher-crank  pin,  a  is  the  pusher,  &  is  the  latch,  c  is 
the  pusher  crank,  d  is  the  valve,  e  is  the  valve  seat,  /  is  the  lifter,  g  is  the 
trip  cam,  h  is  the  trip-cam  yoke,  i  is  the  valve  stem  and  /  is  the  head. 


68  VALVE   SETTING 

It  will  be  noticed  that  the  pusher  a  just  engages  the  edge  of  the  plate 
on  the  latch  &,  with  the  pusher  crank  c  at  the  top  end  of  its  travel  and  the 
eccentric  the  same.  Whenever  the  eccentric,  pusher  crank,  and  pusher  are 
in  the  position  here  shown,  the  valve  d  should  be  lapped  over  the  ports  of 
the  valve  seat  e  as  shown. 

When  the  latch  b  and  the  pusher  a  just  engage  at  the  point  shown,  the 
lifter  /  is  raised  by  the  trip  cam  g  to  the  highest  working  position,  and  the 
valve  will  not  open.  In  order  to  open  full  port,  the  lifter  must  lower  the 
latch  so  that  its  bottom  edge  will  be  along  the  line  H  H  and  the  pusher 
plate  can  engage  it  up  to  the  point  X,  where  it  will  have  the  valve  open 
full  port,  as  shown  in  Fig.  66,  which  shows  the  essential  parts  to  note  of  the 
same  gear  as  in  Fig.  65.  The  same  letters  are  used  to  denote  the  same 
parts  as  in  Fig.  65. 

By  reference  to  the  eccentric  circle  it  will  be  noted  that  the  eccentric 
is  at  E,  or  the  bottom  of  its  travel,  and  the  pusher  crank  the  same.  The 
latch  b  has  been  allowed  to  fall  to  the  position  along  the  line  F  F  in  Fig. 
65,  and  so  the  pusher  has  moved  everything  along  to  the  outside  end  of  the 
valve  travel  where  the  ports  are  full  open  and  the  valve  is  on  the  point  of 
being  released  to  cut-off. 

Fig.  67  is  a  detail  of  the  trip  cam  g  (Fig.  65).  This  cam  is  connected 
to  the  governor  rod  at  A  and  pivots  on  its  pin  at  B  in  the  cam  yoke.  When 
the  governor  is  on  its  stop  before  coming  up  to  speed  the  roller  of  the  lifter 
is  as  shown  for  "  full  stroke  "  and  the  valve  will  be  carried  in  full-port 
opening,  as  in  Fig.  66,  before  releasing  for  cut-off.  After  the  engine  is  up 
to  speed  and  the  governor  lifted  from  its  stop,  the  cam  will  be  moved  along 
in  the  direction  that  will  bring  the  lifter  roller  at  any  point  up  to  that 
shown  for  "  short  cut-off."  When  the  roller  reaches  there,  the  valve  is 
traveling  only  enough  to  overcome  the  lap.  If  the  engine  slows  down  and 
the  stop  is  not  set,  the  governor  will  go  low  enough  to  throw  the  trip  cam 
over  so  that  the  lifter  roller  is  up  to  "  safety,"  when  the  valve  will  not 
travel  at  all,  the  latch  being  lifted  so  high  it  will  not  come  in  contact  with 
the  pusher  plate,  as  in  Fig.  65. 

A  mark  is  put  in  the  edge  of  the  flange  of  the  trip  cam,  as  at  C,  Fig.  67, 
and  this  mark  should  come  under  the  center  of  the  lifter  roller,  as  shown, 
when  ready  to  start  up  or  carry  full  stroke.  (Note  the  rules  for  adjust- 
ment given  later.) 

Fig.  68  shows  the  outlet  (exhaust)  valve  and  plug  with  the  valve  gear 
assembled.  This  first  view  shows  the  valve  wide  open  to  ports  on  the  out- 
side end  of  its  movement.  It  will  be  noted  that  the  eccentric  is  on  the 
bottom  center  of  its  travel  and  the  toggle  stub  end  a  is  at  the  lowest  point 
it  reaches  below  the  line  C  C,  and  the  outlet  valve-stem  head  center  b  has 
reached  its  farthest  point  of  travel  toward  the  valve  plug. 

In  Fig.  69  the  eccentric  has  reached  E  on  the  eccentric  circle  and  the 


THE  GREENE-WHEELOCK  ENGINE 


69 


70 


VALVE   SETTING 


toggle  stub  end  has  come  up  toward  the  line  C  C ;  the  point  I  has  reached 
a  position  corresponding  to  the  near  edge  of  the  ports  and  the  valve  has 
just  cut  off  or  closed  for  compression. 

In  Fig.  70  the  eccentric  has  reached  the  poini   K  on  its  i ravel,  and  the 
toggle  links  now  forming  a  straight  line  from  the  end  of  one  to  the  end  of 


the  other,  the  valve  is  lapped  as  shown  wiih  the  point  b  where  it  is.     This 
is  the  extreme  of  travel  for  the  valve  and  stem  in  this  direction. 

In  Fig.  71  the  eccentric  has  reached  the  point  E,  the  top  center  of  its 
travel,  and  the  toggle  stub  end  the  same,  but  the  point  b  has  come  back  on 
its  travel,  as  well  a>  the  valve,  until  they  nearly  open  again.  The  eccentric 


THE   GREENE-WHEELOCK  ENGINE 


71 


continuing  until  it  reaches  E',  in  Fig.  70,  the  point  b  and  the  valve  will 
have  again  lapped,  and  continuing  until  it  reaches  Ef,  Fig.  69,  the  valve 
will  have  come  back-  to  the  position  shown,  or  is  on  the  point  of  release. 


FIG.    70. 


It  will  be  seen  by  this  that  the  valve  moves  four  times  between  the 
points  of  closure  and  opening,  which  is  a  distinctive  feature  of  this  valve. 


72 


VALVE   SETTING 


CONDITIONS  TO  BE  AVOIDED 

There  are  some  general  conditions  which  if  they  existed  on  this  valve 
gear  would  cause  trouble,  and  it  is  well  to  speak  of  these.     If  the  inlet 


FIG.   71. 

eccentric  rod  is  too  long,  the  valve-stem  latch  and  pusher  may  not  engage, 
or  if  they  do,  the  action  may  be  too  early.  If  the  rod  is  too  short,  it  will 
cause  late  action. 

If  the  outlet  eccentric  rod  is  too  long.it  will  cause  the  valve  to  open  too 
quickly,  and  running  back  too  far  will  partially  obstruct  the  ports  and  it 


THE   GREENE-WHEELOCK  ENGINE  73 

will  close  late. ,   If  too  short,  the  opening  will  be  late  and  the  closure  early, 
with  a  reopening  on  the  back  travel. 

The  eccentrics  in  these  illustrations  run  in  the  direction  of  the  arrows, 
but  also  run  opposite  to  suit  the  conditions,  any  change  of  the  position 
of  the  eccentric  on  its  shaft  has  the  same  effect  as  though  the  eccentric 
were  on  the  main  shaft. 


INSTRUCTIONS  FOR  PROPER  SETTING 

The  following  instructions  are  from  the  builders  of  these  engines,  and 
if  adhered  to  will  give  proper  setting  of  the  valves.  The  preceding  illus- 
trations will  aid  to  a  full  understanding  of  these  operations. 

For  reference  and  a  means  of  checking  off  the  action  of  the  valves  it  is 
stated  that  "  A-size "  valves  have  &  -in.  lap,  .with  J  in.  travel,  and  are 
generally  used  on  cylinders  up  to  and  including  16  ins.  in  diameter; 
"  B-size  "  valves  have  -ft-in.  lap,  with  1-J-in.  travel,  and  are  generally  used 
on  cylinders  from  18  to  26  ins.  in  diameter,  inclusive;  "C-size"  valves 
have  ^-in.  lap,  with  If-in.  travel,  and  are  used  on  cylinders  from  28  ins. 
in  diameter  upward. 

When  starting  to  adjust  the  valves,  first  have  all  eccentrics  loose  on  the 
cylinder  shaft,  and,  second,  determine  the  direction  the  cylinder  shaft  is 
to  run,  -and  always  rotate  the  eccentrics  in  the  same  direction,  whether 
loose  on  the  shaft,  or  when  the  shaft  and  eccentrics  turn  together. 

To  ADJUST  THE  TRAVEL  OF  THE  STEAM  VALVES 

On  the  edge  of  the  pusher  crank  (Fig.  72)  a  line  is  made  in  the  shop, 
and  on  the  side  of  the  plug  head,  next  to  the  pusher  crank,  a  correspond- 
ing line  is  made  (where  the  arrow  points).  When  the  line  on  the  pusher 
crank  corresponds  exactly  with  the  line  on  the  side  of  the  plug  head,  the 
pusher  plate  is  vertical,  as  in  Fig.  65.  This  is  its  most  backward  position. 

Adjust  the  eccentric  rod  for  this  valve  to  such  a  length  that  in  turning 
the  eccentric  around  on  the  shaft  the  line  on  the  edge  of  the  pusher  crank 
comes  back  to  correspond  exactly  with  the  line  on  the  plug  head  at  each 
revolution.  Then,  by  shimming,  adjust  the  bridge-supporting  trip  cam 
(shim  where  the  arrows  in  Fig.  73  denote),  so  that  the  steam  valve  will 
travel  J  of  an  inch  on  "  A  size,"  1  -J  ins.  on  "  B  size,"  and  If  ins.  on 
"  C  size,"  but  bear  in  mind  that  the  varve  must  trip  at  the  end  of  its 
travel  and  the  bridge  must  not  be  so  low  that  the  valve  will  carry  the  full 
stroke  without  tripping.  The  roller  of  the  lifter  must  be  in  position  for 
full  travel,  as  shown  in  Fig.  67. 


74 


VALVE   SETTING 


To  SET  THE  STEAM  VALVES 

On  the  steam-valve  stem  four  scratch  lines  are  made.  These  lines 
represent  the  valve  on  its  lap,  the  valve  just  opening,  the  valve  wide  open, 
and  the  valve  pushed  in  until  it  strikes  the  plug.  With  each  valve  gear  a 
steel-wire  tram  (a,  Fig.  74)  is  sent.  Just  above  the  valve  stem  on  the 
plug-head  casting  a  prick-punch  mark  will  be  found.  Loosen  up  the  inlet 
stem  head  (/,  Fig.  65)  on  the  stem,  then  shove  the  valve  back  until  it 
strikes  the  plug.  If  the  valve  is  set  correctly,  the  tram  with  one  end  in 
the  mark  on  the  plug-head  casting,  as  shown  in  Fig.  74,  should  with  the 
other  end  meet  the  first  scratch  line  on  the  valve  stem  (nearest  the  out- 
side end  of  stem).  If  the  point  of  the  tram  does  not  coincide  with  this 


FIG.   72. 


FIG.   73. 


\L 


FIG.    74. 


FIG.   75. 


line,  the  valve  stem  should  be  screwed  in  or  out  until  it  does.  The  valve 
should  then  be  let  back  so  that  the  dasher  strikes  the  head,  and  the  inlet 
stem  head  be  brought  back  against  the  pusher  plate  when  the  pusher  plate 
is  vertical,  as  in  Fig.  65,  leaving  ^-in.  clearance  between  the  pusher 
and  latch  plates.  It  will  then  be  found  that  the  point  of  the  tram  will 
correspond  with  the  fourth  mark  on  the  stem,  with  the  valve  closed,  as  in 
Fig.  65. 

When  the  valve  is  moved  forward  so  that  the  tram  point  corresponds 
with  the  third  line  on  the  stem,  the  valve  is  just  closing  or  openin.*:.  and 
when  moved  farther  so  that  it  corresponds  with  the  second  line,  the  valve 
is  wide  open.  The  travel  of  the  valve  should  be  between  the  second,,  third, 


THE   GREENE-WHEELOCK   ENGINE  75 

and  fourth  points  spoken  of,  and  it  should  trip  just  as  the  tram  point  cor- 
responds with  the  second  line  from  the  outside  end.  Then,  with  the  piston 
on  dead  center,  the  eccentric  should  be  revolved  on  the  shaft  to  bring  the 
steam  valve  ^2  °f  an  incn  °Pen  on  the  crank  end  and  -fa  of  an  inch  on 
the  head  end.  The  eccentric  should  then  be  clamped  to  the  shaft,  and  the 
valve  is  set. 

To  ADJUST  THE  EXHAUST  VALVES 

On  the  outside  of  the  plug  head,  where  the  arrow  points  in  Fig.  75, 
are  four  prick-punch  marks.  On  the  outside  of  the  outlet  stem  head  where 
the  tram  rests  is  another  prick-punch  mark.  This  is  for  one  point  of 
tram. 

To  ADJUST  VALVES  FOR  LAP 

The  eccentric  rod  should  be  disconnected  from  the  eccentric.  Shove 
the  valve  back  as  far  as  it  will  go.  With  the  valve  in  this  position,  the 
outside  end  of  the  tram  should  fall  into  the  fourth  mark  on  outside  of  the 
plug  head  nearest  the  cylinder.  If  it  does  not,  loosen  up  the  nut  holding 
the  outlet  stem  head,  and  screw  the  stem  in  or  out  sufficiently  to  make  the 
tram  come  up  into  the  fourth  mark.  Then  tighten  up  the  nut  holding  the 
outlet  stem  head,  connect  the  eccentric  rod  to  the  eccentric,  lengthen  or 
shorten  this  eccentric  rod  so  that  the  travel  of  the  valve  due  to  one  revolu- 
tion of  the  eccentric  will  move  the  tram  from  the  first  to  the  third  prick- 
punch  mark,  and  no  farther. 

The  eccentric  should  then  be  set  so  that  when  the  piston  is  about  5 
ins.  from  the  end  of  the  return  stroke,  the  exhaust  valve  should  have 
just  closed,  as  in  Fig.  69,  and  the  tram  point  would  fall  into  the  second 
mark  on  the  plug  head. 

As  these  valves  must  be  set  while  the  valves  are  out  of  sight,  a  strict 
adherence  to  these  rules  of  adjustment  must  be  followed,  care  being  taken 
to  be  accurate,  but  Figs.  65,  66,  67,  68,  69,  70,  and  71  will  help  to  a 
clear  understanding  of  what  is  done  in  this  adjustment  and  subsequent 
operation. 


VII 
THE    BROWN    ENGINE 

THE  engine  is  provided  with  two  steam  valves  and  two  exhaust  valves 
of  the  flat  multiported  type,  each  set  being  operated  by  a  separate  eccen- 
tric and  all  independently  adjustable.  The  steam  valves  are  placed  on  the 


FIG.   76. 


side  of  the  cylinder  and  the  exhaust  at  the  bottom,  the  latter  affording 
an  ideal  water  drain,  as  shown  in  Fig.  76,  which  is  a  section  through 
the  valves  and  cylinder.  The  operation  of  the  steam  valves  can  best  be 

76 


THE  BROWN   ENGINE 


77 


seen  by  referring  to  Fig.  77,  which  shows  the  position  occupied  by  the 
parts  at  the  commencement  of  the  piston  stroke.  The  eccentric  is  con- 
nected to  the  steam  lever  B,  on  the  lower  arm  of  which  is  the  steel  lifting 
block  A  which  has  just  engaged  the  latch  C.  This  is  journaled  on  a  pin 
on  the  guide  D  of  the  steam-valve  stem. 

It  is  evident  that  if  the  eccentric  draws  the  arm  B  toward  the  crank 
shaft  the  block  A  will  be  raised  and  carry  with  it  the  latch  and  guide, 
causing  the  valve  to  open.  This  upward  movement  continues  until  the 


FIG.    77. 

tail  of  the  latch  comes  into  contact  with  the  trip  lever  E,  which  causes 
the  latch  to  release  the  block  and  allows  the  valve,  with  the  stem  and 
guide,  to  fall  to  their  initial  position,  thus  cutting  off  suddenly  the  admis- 
sion of  steam.  A  steam  pressure  equal  to  th*at  on  an  area  equal  to  the 
valve  stem  also  assists  to  close  the  valve,  whose  fall  is  cushioned  by  the 
dashpot  F,  the  amount  of  cushion  being  regulated  by  the  cock  H.  The 
trip  lever  E  is  carried  by  the  trip  shaft  (7,  which  is  connected  to  and 
actuated  by  the  governor. 

The  action  of  the  exhaust  is  shown  in  the  plan  view,  Fig.  78.     The 
exhaust  sliding  bar  A  is  actuated  by  the  eccentric  and  is  connected  by 


78 


VALVE   SETTING 


the  link  B  and  the  lever  C  to  the  exhaust-valve  stem  guide  D,  which  is 
connected  to  the  valve  by  the  stem  E.  The  manner  of  transferring  the 
motion  of  A  to  the  valve  is  quite  apparent,  but  it  should  be  noticed  that 

the  arrangement  gives  the  greatest 
velocity  of  valve  movement  at  the 
points  of  opening  and  closing 
and  provides  a  long  dwell  between 
these  points. 

The  governor  now  provided 
with  these  engines  is  of  the  type 
shown  in  Figs.  79  and  80,  the  first 


FIG   7g 


showing  the  construction  of  the 
governor  and  the  second  its  rela- 
tion to  the  trip  shaft  and  other 
parts  of  the  engine. 

The  centrifugal  action  of  the 

two  weights  A  and  B,  Fig.  79,  is  resisted  by  the  springs,  but  their  out- 
ward motion  rotates  the  sleeve  C,  which  has  a  diagonal  slot  in  which  is 
fitted  a  roller  D  on  a  pin  fast  to  the  central  stem  E.  The  central 


stem  is  by  this   action    forced    io    the   left    in    ih<-   dircci  ion   of   iis   length, 
and  this  moves   the   doiihle  lever  F  to  which  the  stem  is  connected  out- 


THE   BROWN   ENGINE 


79 


side  the  governor  case.  The  connection  of  the  double  lever  F  to  the 
trip  shaft  is  shown  in  Fig.  80,  in  which  is  also  shown  the  connection 
to  the  dashpot,  and  a  stop,  with  the  handle  in  a  vertical  position,  for 
checking  the  outward  motion  of  the  stem.  From  the  description  of  the 
action  of  the  steam-valve  gear,  it  is  evident  that  a  rotation  of  the  trip 
shaft  causes  the  trip  lever  E,  Fig.  77,  to  release  the  latch  earlier  or 
later  in  the  stroke,  according  to  the  load,  and  so  vary  the  point  of  cut-off. 
An  extra  movement  of  -^  in.  of  the  stem  beyond  its  extreme  governing 


FIG.  80. 

position  operates  a  safety  stop  which  does  not  allow  the  latch  to  engage 
the  lifting  block  and  causes  the  steam  valve  to  remain  seated  and  so  shut 
off  steam  completely.  Its  mode  of  operation  will  be  apparent  from  what 
follows. 

It  is  seen  that  this  gear  has  the  quick  opening  and  release  features, 
and  the  use  of  separate  eccentrics  for  the  steam  and  exhaust  valves  allows 
separate  adjustment  for  each  and  permits  of  a  wide  range  of  cut-off  and 
compression.  The  directions  for  setting  the  valves  may  be  stated  as 
follows : 

The  first  requisite  is  the  proper  adjustment  of  the  four  valve  stems 
to  secure  the  necessary  lap  on  each  valve. 

Beginning  with  the  steam  valves,  remove  the  guide  box  A,  Fig.  81, 


80 


VALVE   SETTING 


and  on  the  valve-gear  bracket  a  scratch  mark  B,  prick-punched  at  each 
end,  will  be  found.  Now  disconnect  the  dashpot  connections  from  the 
steam-valve  stem  guide  D  and  allow  the  valve  to  drop  as  far  as  it  will 
go,  and  then  adjust  by  turning  the  valve  stem  in  or  out  of  the  valve  nut 
until  the  distance  between  the  scratch  mark  B  on  the  valve-gear  bracket 

and  the  bottom  of  the  brass  drip 
cup  C  is  the  exact  width  of  a  steel 
gauge,  or   J   in.     Then   make  the 
/7        T       ;  r\  stem  fast  to  the  guide  by  means  of 

I IT  the  nuts  at  E. 

The  dashpot  stem  G  should  then 
be  adjusted  until  the  top  prick- 
punched  scratch  mark  on  the  guide 
D  just  shows  above  the  top  of  the 
guide  box.  Tighten  the  nut  on  the 
dashpot  stem.  Make  these  adjust- 
ments on  both  steam  valves.  Now 
turn  the  full  side  of  the  steam 
eccentric  on  the  forward  or  dead 
center  farthest  from  the  cylinder, 
having  first  seen  that  the  dashpot 
on  the  crank-end  steam  valve  is 
properly  seated.  When  the  eccen- 
tric occupies  the  dead  center,  the 
lifting  block  A,  Fig.  77,  on  the 
crank  end  should  then  have  just 
engaged  the  latch,  with  perhaps  -fa- 
in.  clearance.  If  this  is  not  the 
case,  the  eccentric  rod  should  be 
adjusted  until  this  clearance  is  ob- 
tained. When  the  eccentric  occu- 
pies the  dead  center  nearest  the 

cylinder,  see  that  the  foregoing  conditions  are  fulfilled  at  the  head  or 
end  of  the  cylinder  farthest  from  the  crank  shaft.  If  such  is  not 
the  case,  adjustment  must  be  made  by  the  right  and  left  rod  connect- 
ing the  two  steam  levers  until  the  proper  clearance  is  obtained  on  the 
head  end. 

Now  have  the  eccentric  turned  around  on  the  shaft  and  see  that  both 
valves  are  alternately  raised  an  equal  distance,  which  will  be  the  case  if 
the  adjustments  have  been  properly  made. 

Place  the  crank  and  the  full  side  of  the  eccentric  on  the  dead  center 
nearest  the  cylinder.  The  lifting  block  should  have  now  just  engaged  the 
latch  on  the  head  end.  Have  the  eccentric  turned  around  on  the  shaft 


FIG.   81. 


THE  BROWN   ENGINE  81 

in  the  direction  in  which  the  engine  is  to  run  until  the  valve  opens  the 
ports  the  amount  of  the  lead,  which  should  not  exceed  -g*j  in.,,  unless  it  is 
positively  known  that  the  engine  will  run  better  with  more  lead.  Have 
the  eccentric  fixed  to  the  shaft  at  this  point.  The  amount  of  lead  may 
be  accurately  determined  by  removing  the  upper  head  of  the  valve  chests 
and  measuring  the  lead  by  means  of  pieces  of  thin  steel  -^  in-  thick. 
The  end  of  the  steel  strip  is  to  be  placed  against  the  valve  seat  while  the 
eccentric  is  being  slowly  turned  around  on  the  shaft.  As  soon  as  the 
strip  enters  the  port  the  valve  will  have  opened  -^  in. 

Have  the  crank  turned,  in  the  direction  it  is  to  run,  to  the  opposite 
dead  center  or  crank  end. 

The  opposite  steam  valve  should  now  have  opened  the  port  the  amount 
of  the  lead,  which  it  will  do  provided  the  work  of  equalizing  the  move- 
ments of  the  valves  has  been  properly  done.  If  the  lead  is  found  to  be 
correct,  the  eccentric  must  then  be  permanently  fixed  in  the  position  in 
which  it  will  now  be  found  on  the  shaft. 

The  movement  of  the  exhaust  valves  is  now  to  be  equalized  in  the 
same  manner  as  for  the  steam  valves.  Marks  will  be  found  on  the  ex- 
haust-valve stem  guide  D  and  guide  box  F,  Fig.  78,  showing  the  position 
of  the  valves,  or  should  the  marks  have  become  obliterated,  the  valves 
may  be  seen  by  removing  the  valve-chest  bonnets,  and  by  the  aid  of  pieces 
of  thin  steel  their  exact  location  may  be  determined,  the  same  as  with 
the  steam  valves. 

To  determine  the  proper  length  of  the  exhaust- valve  stem,  draw  the 
valve  forward  until  it  strikes.  Screw  the  valve  stem  into  the  valve  nut 
until  the  marks  H  and  I  come  together,  then  make  the  nut  fast  at  L. 
The  lines  J  and  K  show  .the  lap  of  the  valve.  G  and  J  when  together 
show  the  opening  line. 

To  set  the  exhaust  valves,  mark  the  guides  on  the  frame  at  each  end, 
varying  from  2J  ins.  for  the  small  engines  to  3  or  3J  ins.  for  the  larger 
ones,  from  the  full  stroke  of  the  crosshead.  Then  have  the  crank  turned 
in  the  direction  the  engine  is  to  run  until  the  crosshead  reaches  one  of 
these  marks. 

Assume  that  the  exhaust  eccentric  is  on  the  dead  center  nearest  the 
cylinder  and  that  the  crosshead  has  reached  the  line  on  the  guides  nearest 
the  cylinder.  The  exhaust  eccentric  is  now  to  be  turned  around  on  the 
shaft  in  the  direction  the  engine  is  to  run  until  the  exhaust  valve  on  the 
head  end  just  closes  the  port  or  until  the  lines  G  and  J  come  together. 
Fix  the  exhaust  eccentric  to  the  shaft  at  this  point.  Then  have  the  crank 
turned  in  the  direction  it  is  to  run  until  the  crosshead  reaches  the  line 
at  the  opposite  end  of  the  guides,  when  the  exhaust  valve  at  that  end  of 
the  cylinder  should  have  just  closed  the  port  also. 

If  it  does,  the  compression  will  then  commence  when  the  piston  reaches 


82  VALVE   SETTING 

a  point  from  the  end  of  the  stroke  corresponding  to  the  distance  marked 
on  the  frame  guides. 

The  proper  amount  of  compression  and  lead  will  have  to  be  finally 
determined  by  an  indicator  after  the  engine  has  been  started  and  run 
under  working  conditions.  This  is  recommended  in  every  case. 

If  an  engine  is  to  be  run  condensing,  it  will  require  more  compression 
than  an  engine  running  noncondensing. 

After  both  sets  of  valves  have  been  properly  adjusted  attention  should 
be  given  the  governor. 

Loosen  the  governor  springs  until  the  weights  can  be  readily  moved 
from  one  position  to  the  other  by  means  of  the  central  stem.  Now  press 
the  stem  in  until  the  weights  are  in  their  outer  position,  and  block  them. 
Loosen  the  set  screw  in  the  governor  connection  lever  on  trip  shaft  and 
move  the  trip  lever,  E,  Fig.  77,  nearest  the  governor,  which  is  permanently 
fastened  to  the  trip  shaft,  either  toward  or  away  from  the  latch  as  the  case 
may  require,  until  the  crank-end  steam  yalve  upon  being  raised  will  cut  off 
when  the  second  prick-punched  scratch  mark  on  the  guide  D,  Fig.  81, 
appears  at  the  top  of  guide  box.  Then  tighten  the  set  screw  in  the  gover- 
nor lever  on  the  trip  shaft.  That  is,  with  the  governor  weights  in  their 
outer  position,  the  steam  valve  is  only  allowed  to  lift  enough  to  just  un- 
cover the  lap.  The  lap  is  the  distance  between  the  first  and  second  scratch 
marks. 

Place  the  small  handle  on  the  front  of  governor  in  a  vertical  position 
and  pull  the  stem  out  until  it  is  stopped  by  the  handle,  which  will  bring 
the  governor  weights  to  their  inner  position.  The  steam  valve  now  being 
raised  should  not  be  cut  off  until  the  third  prick-punched  scratch  mark 
shows  at  the  top  of  the  guide  box,  or  -fa  in.  less  than  the  full  throw  of 
the  short  horizontal  arm  of  the  steam  lever  B.  The  movements  of  the 
two  steam  valves  may  now  be  equalized  by  means  of  the  taper  pin  L,  in 
the  trip  lever  of  the  head-end  steam  valve.  This  can  be  seen  in  Fig.  77, 
and  acts  as  a  taper  key.  By  loosening  the  set  screw  and  driving  the  pin 
in,  the  cut-off  is  shortened;  by  driving  it  out,  the  cut-off  is  lengthened. 

The  taper  pin  is  not  used  with  the  latest  design,  the  movements  of 
the  two  valves  being  equalized  by  means  of  the  two  knurled  finger  screws 
on  the  yoke  made  fast  to  the  trip  shaft  at  the  head-end  trip  lever,  which  is 
itself  loose  on  the  trip  shaft. 

In  setting  the  safety  stop,  proceed  as  follows:  With  the  small  safety 
stop  handle  in  a  horizontal  position  and  the  central  stem  pulled  out  as 
far  as  it  will  go,  the  governor  balls  are  allowed  to  reach  an  extreme  point 
beyond  their  inner  governing  position,  which  imparts  to  the  central  stem 
an  extra  -fo-m.  motion  beyond  its  working  limit.  Block  the  governor  in 
this  position.  Now  screw  J,  Fig.  77,  in  until  the  lower  end  of  the  pawl 
K  strikes  the  tail  of  the  latch  C,  and  the  steel  on  upper  end  of  this  latch 


THE   BROWN   ENGINE  83 

is  just  thrown  out  of  engagement  with  the  lifting  block  A.  Make  the 
check  nut  tight  on  the  screw  J. 

This  adjustment  being  made  on  both  ends  of  the  cylinder,  each  valve 
should  be  raised  two  or  three  times  to  see  that  proper  clearance  has  been 
given  between  the  steel  on  the  latch  and  the  lifting  block,  so  that  the 
latch  cannot  hook  on  at  this  point. 

Thus,  should  the  governor  belt  break,  or  by  any  other  cause  the  gov- 
ernor balls  be  allowed  to  reach  their  extreme  inner  position,  the  steam 
valves  remain  seated,  cutting  off  any  further  supply  of  steam  to  the 
cylinder. 

After  setting  the  valves  and  safety  stop,  the  small  handle  on  governor 
should  be  moved  to  the  horizontal  position  and  LEFT  THERE  until  such  time 
as  further  valve  setting  is  necessary.  In  that  position  the  safety  stop  is 
in  operation  at  all  times.  Of  course,  after  shutting  down  this  will  block  the 
steam  valves  from  lifting  and  prevent  starting  up  until  some  change  is  made 
in  the  position  of  governor  balls  or  other  parts.  All  that  is  necessary  is  to 
loosen  the  small  binding  handle  on  governor  link  and  turn  the  pin,  which 
is  eccentric  in  the  link,  half  around,  in  which  position  the  trip  levers  are 
given  |  in.  advance  ahead  of  the  governor.  After  starting  up  and  nearly 
reaching  speed,  turn  eccentric  pin  to  original  position  and  lock  it. 


VIII 
THE    McINTOSH    &    SEYMOUR    ENGINE 

THE  valves  of  this  engine  are  of  the  multiported  flat  gridiron  type, 
located  at  the  four  corners  of  each  cylinder  in  much  the  same  fashion 
as  the  Corliss.  There  are  two  main  steam  valves  and  two  main  exhaust 
valves,  in  addition  to  which  there  are  two  riding  cut-off  or  auxiliary 
valves  placed  on  top  of  the  main  steam  valves.  The  valves  are  all 
driven  by  positive  valve  gear,  consisting  of  plain  links  and  rockers, 
operating  with  a  toggle  motion,  and  their  movement  is  crosswise  of  the 
cylinder  bore. 

Figs.  82,  83,  84,  and  85  show  in  outline  the  arrangement  of  the  valves 
and  gear  on  a  horizontal  engine.  The  main  valves,  both  steam  and  ex- 
haust, are  driven  by  an  oscillating  shaft  M,  which  derives  its  motion  by 
a  rocker  R  and  link  L  from  a  fixed  eccentric  F  on  the  engine  shaft,  as 
shown  by  Fig.  83.  This  gives  fixed  points  of  opening  and  closing,  and 
governs  the  admission  of  steam  and  the  opening  and  closing  of  the  ex- 
haust. The  connection  between  the  sha'ft  M  and  the  main  steam  and 
exhaust  valves  is  shown  in  the  cross  section,  Fig.  84,  and  it  will  be  seen 
that  these  main  valves  can  be  adjusted  to  vary  independently  the  admis- 
sion, the  release,  or  the  compression.  In  practice  the  main  steam  valve 
is  set  to  close  when  about  60  per  cent,  or  more  of  the  stroke  has  been 
completed,  so  that  steam  may  be  carried  up  to  this  point  unless  cut  off 
earlier  by  the  auxiliary  valve.  The  governor  operates  only  these  auxiliary 
or  cut-off  valves.  This  is  done  through  the  medium  of  the  lower  rock 
shaft  A  and  the  arrangement  of  links  and  bent  lever,  as  shown  in  Fig. 
85.  The  shaft  A  is  driven  from  the  governor  eccentric  G  by  means  of 
the  bell  crank  B  and  link  ?.  The  governor  eccentric  is  arranged  to  revolve 
around  the  shaft  by  the  action  of  the  governor,  as  shown  in  Fig.  82,  in- 
stead of  across  the  shaft,  as  is  more  common  in  shaft  governors.  It  thus 
governs  by  varying  the  angular  advance  of  the  eccentric  in  place  of  chang- 
ing the  travel  of  the  valve.  The  arrangement  is  such  that  when  cut-off 
takes  place  the  cut-off  valve  is  moving  in  an  opposite  direction  to  the 
main  steam  valve,  giving  a  very  rapid  closing  of  the  port  and,  conse- 
quently, the  desired  sharp  corner  on  the  diagram. 

As  the  valves  are  multiported,  only  a  very  small  movement  is  required 

$4 


THE  McINTOSH   &  SEYMOUR  ENGINE 


85 


86 


VALVE  SETTING 


to  give  full  port  opening.     This  varies  from  J  in.  to  1J  ins.  from  the 
smallest  to  the  largest  size  of  cylinder. 

Figs.  86  and  87  show  enlarged  views  of  the  cylinder  and  valve  gear, 


FIG.   86.  — DETAILS  OF   GEAR. 

and  in  connection  with  Figs.  76  and  77  will  allow  a  ready  understanding 
of  the  valve  motion.  (The  detailed  views  are  stripped  as  far  as  possible 
of  unnecessary  details,  such  as  nuts,  housings,  oil  cups,  keys,  etc.)  The 


FIG.   87.  — DETAILS  OF  GEAR. 


stroke  motion  derived  from  an  eccentric  or  any  other  crank  is  of  course 
more  rapid  at  the  center  of  the  travel  than  at  the  ends,  and  advantage  is 


THE  McINTOSH   &  SEYMOUR  ENGINE 


87 


taken  of  this  fact  to  distort  the  motion  received  from  the  eccentric  so  as 
to  secure  a  rapid  movement  at  one  end  of  the  valve  stroke  and  to  retard 
the  motion  at  the .  other  end  of  the  stroke.  This  is  done  by  arranging 
the  oscillating  movement  of  shafts  M  and  A  by  means  of  the  rockers  and 
links  from  the  eccentrics,  so -that  the  pins  P  P,  Fig.  86,  and  p  p}  Fig.  87, 
will  move  slightly  past  the  center  at  the  extreme  of  the  stroke,  as  shown 
by  the  dotted  lines  indicating  the  angular  movement.  The  result  is  that 
at  one  extreme  of  the  travel  pins  P  and  p  are  moving  through  the  flat 
part  of  the  arc  and  give  a  large  horizontal  movement  for  a  small  angular 
motion;  while  at  the  other  extreme  the  pins  move  through  a  considerable 
angle  without  much  in-and-out  motion.  This  is  conveyed  to  the  valves 
by  the  gear  in  such  manner  that 
the  valves  open  and  close  quickly, 
but  remain  practically  still  when 
closed. 

The  greater  part  of  the  valve 
movement  takes  place  when  the 
valve  is  open,  and  at  such  times 
the  valve  is  partially  balanced  or 
relieved  of  the  steam  pressure. 
Consider,  for  instance,  the  cut-off 
valve.  It  will  be  closed  by  the  ac- 
tion of  the  governor  at,  say,  from 
20  to  30  per  cent,  of  the  stroke, 
while  the  main  steam  valve,  upon 
which  it  seats,  will  remain  open 
much  longer.  As  soon  as  the 
edges  of  the  bridges  of  the  cut-off 
valve  project  over  the  ports  of  the  main  valve  the  cylinder  pressure  will 
balance  it  by  the  amount  of  the  projection,  and  this  balancing  will  increase 
as  the  cut-off  bridges  cover  the  main  ports.  The  main  steam  valve  will  be 
similarly  balanced  between  the  cylinder  and  the  cut-off  valve  when  it  closes, 
and  the  exhaust  valve  moves  under  very  little  pressure  at  any  time. 

On  compound  or  triple  engines  the  same  valve  arrangement  is  used 
on  each  cylinder,  the  main  valves  being  driven  by  a  fixed  eccentric,  while 
all  the  cut-off  valves  are  driven  by  the  governor  eccentric,  thus  equalizing 
the  work  on  the  various  cylinders. 

The  main  rock  shafts  M  and  A  are  carried  on  brackets  from  the  lower 
part  of  the  cylinder,  and  the  short  upper  pins  or  shafts  m  and  a  are  car- 
ried by  similar  brackets  at  the  upper  corners  of  the  cylinder. 

Adjustment  is  provided  at  all  wearing  points,  the  links  having  bronze 
boxes  with  key  take-up  (not  shown  in  Figs.  86  and  87),  and  the  rock 
shafts  having  regular  babbitted  and  capped  bearings.  The  valves  and  the 


FIG.   88. 


88 


VALVE   SETTING 


crossheads  c  c,  Fig.  86,  are  arranged  to  wipe  over  and  all  valve  stems  are 
adjustable. 

The  valve  seats  or  grids  are  separate  from  the  cylinder  and  are  put 
in  place  with  scraped  joints,  avoiding  the  use  of  soft  packing.  Valve  cov- 
ers are  provided  over  each  of  the  four  sets  of  -valves,  as  in  Fig.  88. 

As  shown  in  Figs.  86,  87,  and  88,  the  ports  and  clearance  spaces  are 
very  small,  the  total  clearance  in  most  cases  being  less  than  in  the  Cor- 
liss type.  In  a  word,  the  distinctive  features  of  this  valve  gear  are :  Grid- 
iron valves  at  four  points;  the  main  valves  driven  by  a  fixed  eccentric 
and  controlling  admission,  release,  and  compression;  and  the  cut-off  valves 
driven  by  a  governor  eccentric,  controlling  cut-off  by  varying  the  angular 


TRAVEL 

"  -      MAIN  STEAM  VALVE 


FIG. 


89.  —  MAIN  STEAM  VALVE  IN  EXTREME  INNER  POSITION.     AUXILIARY  STEAM 
VALVE  IN  CENTRAL  POSITION. 


advance;  all  driven  by  a  positive  valve  gear  which  permits  of  high  rotative 
speeds  and  dispenses  with  dashpots  and  releasing  gear. 

Figs.  89  and  90  are  enlarged  views  of  the  valves  and  grids,  and  show 
the  shape  of  valves  and  ports,  the  laps  and  the  attachment  of  valve  stems  ; 


FIG.   90. —  EXHAUST  VALVE   IN   EXTREME   INNER   POSITION. 

while  Figs.  91,  92,  and  93,  in  connection  with  Figs.  82,  83,  84,  and  85, 
illustrate  the  instructions  for  setting  the  valves. 


SETTING  THE  VALVES 

As  a  preliminary  to  setting  the  valves  it  is  necessary  to  know  the 
strokes,  laps,  and  leads  of  all  valves,  the  points  of  cut-off  for  both  main 
and  auxiliary  valves  and  the  point  of  exhaust  closure  or  compression. 


THE  McINTOSH   &  SEYMOUR  ENGINE  89 

These  vary  with  the  individual  engine  and  must  be  obtained  from  the 
maker  in  each  case.  The  strokes,  laps,  and  leads  will  be  given  in  inches, 
and  the  points  of  cut-oft'  and  compression  will  be  given  either  in  fractions 
of  the  stroke  or  in  inches  of  the  stroke  measured  from  the  dead-center 
point.  Having  these  figures,,  the  first  operation  is  to  set  the  main  valves, 
both  exhaust  and  steam.  First  turn  the  engine  over  slowly  and  by  means 
of  link  L,  connecting  the  rocker  R  and  shaft  M,  Fig.  83,  adjust  the  angu- 
lar movement  of  shaft  M  until  the  exhaust  valve  shows  exactly  the  proper 
stroke  or  travel.  A  mark  will  be  found  completely  encircling  the  valve 
stems  at  some  point  outside  the  stuffing  box,  as  at  X,  Fig.  91 ;  and  the 
stroke  can  be  measured  by  means  of  this  mark,  either  from  the  face  of 
the  box  or  from  any  other  fixed  point.  As  soon  as  the  stroke  is  fixed, 
set  up  the  lock  nuts  on  link  L  to  prevent  change,  and  by  means  of  link 
S,  Fig.  84  or  86,  adjust  the  stroke  of  the  main  steam  valves.  The  stroke 
of  the  exhaust  valve  is  adjusted  first  because  it  is  directly  connected  to 
shaft  M  by  links  of  fixed  length,  and  the  correct  movement  of  shaft  M 
is  obtained  without  introducing  link  8. 

So  far  no  attention  has  been  paid  to  laps  or  leads,  the  strokes  only 
being  adjusted.  Next,  remove  the  valve  covers  and  screw  the  valve  stems 
in  or  out  of  the  small  crossheads  c  c,  Figs.  84  and  86,  until  the  valves 
show  the  proper  lap. 

Then  place  the  engine  on  the  head-end  dead  center,  and  roll  the  fixed 
eccentric  F,  Fig.  83,  around  the  shaft  until  the  head-end  main  steam 
valve  shows  the  proper  lead  or  is  "  line  and  line/'  if  there  is  no  lead. 
Then  lock  the  eccentric  in  place  by  the  set  screws. 

Before  going  any  further  it  is  well  to  make  a  mark  on  crosshead  and 
guides,  showing  the  head-end  dead  center,  as  in  Fig.  92;  its  use  will  be 
explained  later.  When  this  is  done,  roll  the  engine  over  to  the  crank- 
end  dead  center,  and  if  the  work  has  been  accurately  done  the  crank-end 
main  steam  valve  will  show  the  proper  lead.  Make  another  mark  on  the 
guides  opposite  the  mark  on  the  crosshead;  the  distance  between  this  mark 
and  the  one  formerly  made  will  be  the  stroke  in  inches,  as  shown  by 
Fig.  92. 

Now  measure  forward  on  the  guides,  from  the  head-end  dead  center, 
a  distance  in  inches  equal  to  the  point  of  cut-off  of  main  steam  valve  and 
make  a  mark  R.  (This  distance  is  given  in  inches  by  the  engine  builder.) 
Place  the  engine  on  the  forward  stroke  until  the  mark  on  the  crosshead 
coincides  with  line  R,  as  in  Fig.  92,  the  head-end  steam  valve  should 
come  line  and  line  with  the  port. 

Measure  forward  again  from  the  head-end  dead  center  to  the  point  of 
compression  or  closure  of  the  exhaust  valve,  and  make  another  mark  0 
on  the  guides.  When  the  engine  is  placed  on  the  forward  stroke  so  that 
the  crosshead  mark  coincides  with  mark  0,  the  crank-end  exhaust  valve 


90 


VALVE   SETTING 


THE  McINTOSH   &  SEYMOUR  ENGINE  91 

should  come  line  and  line.  Make  similar  marks  r  and  o  on  the  guides, 
measuring  back  from  the  crank-end  dead  center,  for  the  points  of  main 
valve  cut-off  and  compression  on  the  return  stroke,  as  shown  above  Fig. 
92,  and  by  placing  the  engine  on  the  return  stroke,  check  to  see  that  the 
other  valves  come  line  and  line.  On  all  main  steam-  and  exhaust-valve 
stems  will  be  found  an  encircling  mark  like  that  at  X}  Fig.  91.  This 
trams,  by  a  tram  of  known  length,  with  a  mark  on  the  cylinder  casing 
when  the  valves  are  line  and  line,  thus  making  it  unnecessary  to  remove 
the  valve  covers. 

The  auxiliary  or  cut-off  valves  yet  remain  to  be  set.  Measure  forward 
on  the  guides  and  locate  point  Q,  the  point  of  cut-off  of  the  auxiliary 
valve  as  furnished  by  the  builders;  also  measure  back  from  the  crank- 
end  center  and  locate  the  similar  point  q  for  the  return  stroke.  Adjust 
link  /,  Fig.  82,  and  link  K,  Fig.  85,  to  give  the  proper  stroke  of  the  valve, 
measuring  the  stroke  as  before  by  the  mark  x  on  the  stem.  Then  turn 
the  engine  forward  until  the  crosshead  mark  coincides  with  mark  Q  and 
set  the  head-end  auxiliary  valve  line  and  line  with  the  port  of  the  main 
valve.  Put  the  engine  on  the  return  stroke  to  point  q  and  set  the  crank- 
end  auxiliary  valve  line  and  line  with  the  main  valve,  the  governor  remain- 
ing closed  during  both  operations. 

This  completes  the  valve  setting.  To  facilitate  future  settings,  two 
punch  marks  can  be  made  in  the  rim  of  the  detaching  gear  of  shaft  M 
to  agree  with  a  tram  from  the  cylinder  face,  as  in  Fig.  93,  thus  estab- 
lishing at  a  convenient  point  the  proper  angular  motion  for  the  stroke 
of  the  main  valves.  It  is  of  course  necessary  to  have  all  shaft  bearings, 
links,  rockers,  etc.,  in  good,  snug  working  order  and  free  from  unnecessary 
lost  motion.  In  placing  the  engine  on  the  dead  centers  and  in  turning 
it  over  to  the  several  points  of  the  stroke,  it  is  equally  necessary  to  take  up 
all  "  play  "  or  lost  motion  in  the  direction  of  rotation,  as  would  occur  if 
the  engine  were  actually  turning  over  under  pressure. 


IX 


THE    BUCKEYE    ENGINE 

THE  Standard  Buckeye  engine  is  of  the  two-valve  type,  having  a  bal- 
anced box  main  valve  working  over  a  port  at  each  end  of  the  cylinder^ 


SKELETON  DIAGRAM  OF  VALVES  AND  GEAR 


PLAN 


FIG.    95. 


and  a  flat  cut-off  or  auxiliary  valve  riding  inside  of  the  main  valve.  The 
single  short  port  at  each  end  of  the  cylinder  serves  alternately  for  the  pur- 
poses of  admission  and  exhaust. 

92 


THE  BUCKEYE  ENGINE 


93 


Both  valves  are  driven  by  positive  valve  gear.  The  main  valve  re- 
ceives its  motion  from  a  fixed  eccentric  and  governs  the  admission  and  the 
release  or  compression.  The  cut-off  valve  is  controlled  from  the  governor 
eccentric  and  governs  the  cut-off  only. 

The  elevation  and  plan  of  Figs.  94  and  95,,  and  the  sections  of  Figs. 
96,  97,  98,  and  99,  show  the  arrangement  and  operation  of  the  valves 


FIG.   96.  —  HORIZONTAL  SECTION. 


and  valve  gear.  As  shown  by  Figs.  96  and  98,  the  valve  chest  is  divided 
by  partitions  into  two  separate  and  distinct  parts,  a  steam  chamber  and 
an  exhaust  chamber.  The  main  valve  is  a  flat  hollow  box  of  the  horizontal 
and  vertical  sections  shown  in  Figs.  96  and  99,  set  upright  in  the  exhaust 


FIG.    97. —  VERTICAL   SECTION   A-B. 


chamber  and  working  lengthwise  of  the  cylinder.     It  takes  steam  into  the 
interior  through  the  four  balance  pistons  B,  which  connect  it  with  the 


94 


VALVE   SETTING 


steam  chamber  and  serve  to  hold  it  in  place;  and  steam  is  admitted  to 
the  cylinder  through  ports  p,  which  coincide  at  proper  intervals  with  the 
cylinder  ports  P.  The  exhaust  passes  out  over  the  ends  of  the  valve  di- 
rectly into  the  exhaust  chamber  which  surrounds  the  valve. 

In  Fig.  96  the  engine  is  on  the  head-end  center  and  the  course  of  the 
steam   and  exhaust  is  shown  by  the  arrows.     The  main  valve  is  hollow 


STEAM  CHAMBER 


EXHAUST    CHAMBER 


FIG.   98.  — VERTICAL  SECTION   C-D. 

and  supplies  its  steam  from  the  inside;  its  motion  is  just  opposite  to  the 
piston  movement,  and  its  eccentric  follows  the  crank  instead  of  leading 
it,  as  shown  in  the  skeleton  diagram  of  Fig.  94.  The  balance  pistons  B 
are  packed  in  their  bores  by  spring  rings,  and  have  a  scraped  joint  on  the 
back  of  the  valve;  this  makes  a  steam-tight  passage  from  steam  inlet  to 
cylinder,  irrespective  of  the  remainder  of  the  valve  chest. 

On  the  side  of  the  engine  is  a  rocker  arm,  R,  Figs.  94  and  95,  pivoted 
to  the  frame  at  its  lower  end  A  and  carrying  at  its  upper  extremity  the 


MAIN  VALVE 


FIG.    99. —  VERTICAL    SECTION    E-F. 


pin  or  shaft  a.  One  end  of  this  pin  receives  the  rod  from  the  fixed  eccen- 
tric F,  and  the  other  end  transmits  the  motion  to  the  main  valve,  as  shown 
in  Fig.  95.  The  main  valve  has  thus  a  fixed  travel  and  governs  the  ad- 
mission and  release  just  as  in  an  ordinary  slide  valve  throttling  engine. 


THE  BUCKEYE   ENGINE 


95 


It  is  arranged  to  close  the  cylinder  port  at  some  predetermined  point,  say 
two  thirds  of  the  stroke,  corresponding  to  the  maximum  horse  power  the 
engine  is  expected  to  develop. 

The  cut-off  valve  consists  of  two  narrow  flat  plates  C  C,  Figs.  96,  97, 
and  98,  connected  by  rods  and  riding  over  seats  formed  on  the  back  of 
the  main  valve.  It  is  controlled  from  the  governor  eccentric  through  the 
medium  of  the  two  arms  or  rockers  b  Z>,  pivoted  on  the  main  rocker  arm 
R  at  point  5,  about  midway  of  its  length.  (This  is  shown  in  detail  in 
Fig.  100.) 

The  skeleton  diagram  of  Fig.  94  shows  the  engine  on  the  crank-end 
center,  with  the  governor  eccentric  in  position  for  about  one  quarter 
cut-off.  The  motion  of  the  cut-off  valve  is  seen  to  be  compounded  of  the 


ALVE 

FROM  FIXED  ECC. 


INGS 


FROM  GOV.  ECC. 


FIG.    100. —  SECTION    SHOWING   ROCKER   ARM. 

motions  of  both  fixed  and  governor  eccentrics.  Owing  to  the  fact  that 
its  rocker  is  pivoted  on  the  main  rocker,  it  rides  back  and  forth  with  the 
main  valve;  and  it  plainly  has  also  a  travel  on  the  main  valve,  derived 
from  its  own  or  governor  eccentric.  The  governor,  as  shown  by  Fig.  94, 
operates  by  varying  the  angular  advance  or  by  revolving  eccentric  G 
around  the  shaft  instead  of  across  it;  so  that  the  cut-off  valve  has  a  con- 
stant length  of  travel  on  the  main  valve,  no  matter  what  their  relative 
positions  or  the  point  of  cut-off.  The  main  valve  has  also  a  constant 
travel,  as  it  is  driven  by  a  fixed  eccentric.  This  prevents  the  wearing 
of  shoulders  and  is  therefore  conducive  to  tightness. 

The  extreme  positions  of  the  governor  eccentric  are  45  degrees  or  more 
each  side  of  the  position  of  Fig.  94,  and  the  cut-off  may  thus  take  place 
at  any  point  from  the  beginning  of  the  stroke  up  to  the  maximum  cut-off 
allowed  by  the  main  valve,  according  to  the  position  of  the  governor  and 
the  corresponding  angular  advance  of  eccentric.  The  arrangement  is  such 
that  cut-off  takes  place  near  the  middle  of  the  cut-off  valve  travel,  where 
the  motion  is  fastest,  thus  giving  a  quick  closure  of  the  port.  The  stem 
of  the  main  valve  is  made  hollow  to  admit  the  cut-off  stem,  permitting 


96 


VALVE  SETTING 


attachment  to  each  valve  to  be  made  at  its  center  of  gravity.  The  area  of 
the  balance  pistons  is  sufficient  to  hold  the  valve  to  its  seat  against  the 
cylinder  pressure,  which  is  greatest  during  admission. 

This  cylinder  pressure  becomes  less  and  less  during  expansion,  while 
the  pressure  due  to  the  balance  pistons  remains  constant,  so  that  the  valve 
is  balanced  during  only  a  part  of  its  stroke.  To  counteract  the  excess 
pressure  of  the  balance  pistons  during  expansion,  recesses  or  relief  cham- 
bers, Fig.  96,  are  cut  in  the  valve  seats  and  filled  with  live  steam  from 
the  interior  of  the  valve  through  holes  y,  thus  allowing  the  steam  pressure 
to  get  behind  the  valve  and  balance  it.  Channels  z,  cut  clear  across  the 
valve  face,  prevent  the  steam  from  acting  on  too  great  an  area  and  thus 
overbalancing  the  pistons;  and  at  the  instant  of  admission  the  valve  un- 
covers recess  x,  as  shown  at  the  left  hand  of  Fig.  96,  leaving  the  valve 


EXHAUST  CHAMBER/ 

FIG.    101.  — PISTON    VALVE. 


to  be  balanced  by  the  cylinder  pressure  during  admission.  Small  coil 
springs  behind  the  balance  pistons  hold  the  valve  in  place  while  steam  is 
shut  off  the  engine.  It  is  not  attempted  to  balance  the  valve  entirely; 
enough  excess  pressure  is  allowed  to  hold  the  valve  firmly  to  its  seat. 

Owing  to  the  positive  valve  gear,  or  the  absence  of  releasing  mechan- 
ism, it  is  possible  to  operate  at  any  desired  rotary  speed.  The  engines  are 
made  in  three  types  with  long,  medium,  and  short  strokes,  having  rotary 
speeds  of  60  to  170,  100  to  230,  and  200  to  325  revolutions  per  minute, 
respectively. 

For  tandem-compound  and  cross-compound  engines  the  governor  cut-off 
is  usually  applied  to  both  cylinders,  the  valve  stems  of  both  main  and  cut-off 
valves  being  extended  through  from  one  valve  chest  to  the  other. 

For  very  high  initial  pressures  and  for  the  high-pressure  cylinders  of 
compound  engines,  the  balanced  piston  valve  of  Fig.  101  is  frequently  used. 
It  has  the  same  general  features  as  the  balanced  flat  valve  of  Fig.  96. 
The  main  valve  consists  of  two  hollow  cylinders  connected  by  a  series  of 
bars,  and  having  the  outer  ends  closed.  It  takes  steam  into  the  interior 


THE   BUCKEYE   ENGINE 


97 


through   the  .spaces   between   the   rods    and   admits   it   into   the   cylinder 
through  ports  p,  as  shown.     The  exhaust  passes  out  over  the  ends  of  the 
valve.     The  cut-off  valve  C  consists  of  two 
short,  hollow  pistons  or  cylinders,  rigidly 
connected,  and  working  over  ports  p,  on  the 
inside  of  the  main  valve.     Both  main  and 
cut-off  valves  are  made  tight  by  spring  rings. 
The  valve  gear  is  identical  with  that  pre- 
viously described. 

To  secure  quick  admission  and  release 
with  a  small  valve  travel,  multiported  valves  are  sometimes  used.  This  is 
usually  done  only  on  long-stroke  engines  of  large  size,  simple  valves  with 
sufficient  travel  being  preferred  on  small  high-speed  engines.  Fig.  102 
shows  a  double-ported  main  valve. 


FIG.  102. 


SETTING  THE  VALVES 

The  operation  of  setting  the  valves  is  quite  simple.  First  see  that 
pin  a  at  the  upper  end  of  rocker  R  vibrates  an  equal  distance  each  side 
of  its  central  position.  This  may  be  done  by  plumbing  up  from  pivot 
A,  Fig.  103,  and  measuring  the  distances  a  B  and  a  C,  which  represent 
the  horizontal  travel  of  the  pin.  If  these  are  not  equal,  adjust  the  fixed 
eccentric  rod  /  until  they  are  equal.  For  future  reference,  marks  indi- 
cating the  corresponding  positions  may  be  made  on 
the  hub  or  other  convenient  point,  as  shown,  if  they 
are  not  already  there. 

Next  place  the  engine  on  the  head-end  center,  be- 
ing careful  to  take  up  all  lost  motion  in  the  direction 
of  rotation. 

Unhook  the  fixed  eccentric  /  and  place  the  rocker 
arm  R  in  its  central  position.  The  main  valve 
should  then  be  in  its  central  position  on  the  valve 
seat.  JSTow  roll  fixed  eccentric  around  the  shaft,  to 
such  a  position  behind  the  crank  that  the  next  valve 
movement  will  be  away  from  the  crank,  or  contrary 
to  the  forward  stroke  of  the  piston,  as  shown  in  Fig. 
104;  and  couple  the  eccentric  rod  f  to  pin  a  of  the 
rocker.  Then  leaving  the  engine  on  the  dead  center, 
roll  eccentric  F  further  around  the  shaft  toward  the 
crank  until  the  outer  edge  of  valve  port  p  overlaps 
the  inner  edge  of  cylinder  port  P  by  the  amount  of 
the  lead,  or  until  the  port  edges  are  line  and  line,  if  there  is  no  lead.  The 
valve  ports,  crank,  and  eccentric  will  now  occupy  a  position  about  as  Fig. 


FIG.    103. 


98 


VALVE  SETTING 


/ 


i 


THE  BUCKEYE  ENGINE  99 

105.  Lock  the  eccentric  F  in  place  and  roll  the  engine  around  to  the  crank 
center ;  if  the  work  has  been  accurately  done,  the  valve  will ,  show  proper 
lead  on  the  crank  end.  Slight  adjustments  may  be  made  by  the  valve  stem. 
This  completes  the  setting  of  the  main  valve. 

If  the  eccentric  is  but  slightly  out  of  place,  it  will  be  necessary  only 
to  adjust  the  eccentric  to  show  proper  lead.  For  the  cut-off  valve,  first 
see  that  it  makes  the  proper  length  of  stroke  on  the  main  valve,  adjust- 
ing eccentric  rod  g  until  it  does.  Then  with  the  engine  on  the  crank- 
end  center,  allow  the  governor  to  come  to  rest  on  its  inner  stops.  This 
will  revolve  eccentric  0  backward  on  the  shaft  until  its  center  about  coin- 
cides with  the  crank.  This  is  shown  by  Fig.  94,  where  the  governor  is  in 
an  intermediate  position,  the  dotted  lines  representing  the  extreme  inner 
and  outer  positions  of  the  governor  arms.  The  exact  position  of  eccentric 
G  when  the  governor  is  at  rest  will  be  fixed  by  the  design  of  the  engine; 
for  condensing  engines  it  may  be  a  little  ahead  of  the  crank,  while  for 
aeavily  loaded  engines  not  subject  to  great  fluctuations  of  load,  it  may 
be  a  little  behind  the  crank. 

Under  ordinary  conditions  the  crank  and  the  governor  eccentric  should 
pass  the  dead  center  at  the  same  time,  in  the  same  direction. 

Then  with  the  engine  on  the  crank-end  center  and  the  eccentric  G 
coinciding  with  the  crank,  the  cut-off  valve  should  be  in  its  extreme  left- 
hand  or  head-end  position,  since  the  rockers  b  reverse  the  motion  of  the 
eccentric.  If  the  valve  does  not  occupy  this  position,  adjust  the  valve 
stem  until  it  does.  With  crank  and  eccentric  still  coincident,  turn  the 
engine  over  to  the  head-end  center  and  see  that  the  cut-off  valve  is  in  its 
extreme  crank-end  position.  The  point  of  cut-off  is  then  determined  by 
the  angular  advance  of  the  eccentric,  which  in  turn  depends  upon  the 
adjustment  of  the  governor.  Roughly  speaking,  for  one  quarter  cut-off 
the  governor  should  occupy  such  a  position  as  to  bring  eccentric  G  about 
90  degrees  ahead  of  the  fixed  eccentric. 


IX—  (Continued) 

THE    BUCKEYE    ENGINE— Continued 
THE  BUCKEYE  PISTON  VALVE 

THE  first  part  of  this  chapter  treats  of  the  older  Buckeye  engine  with 
box  type  of  valve.  In  this  part  of  the  chapter  we  wish  to  give  the  build- 
ers instructions  for  setting  the  valves  on  their  newest  type  of  piston  valve 
with  inside  cut-off. 

Fig.  105A  gives  a  sectional  view  of  the  cylinder  and    valves  of    this 
engine  with  the  latter  in  position.     It  will  be  seen  that  the  valve  setting 


FIG.   105A. 

involves  the  same  principles  as  explained  for  the  box  type  of  Buckeye  valve, 
but  as  there  are  several  points  of  difference  in  the  details,  the  following 
instructions  will  be  of  value  and  necessity  to  the  operating  engineer : 

SETTING  PISTON  VALVES 

The  foregoing  instructions  for  setting  side  valves  are  to  a  certain  ex- 
tent inapplicable  to  piston  valves,  as  none  of  the  events  can  be  observed 
by  removing  plates  or  covers,  except  where  a  guide  stem  works  in  a  re- 
movable bonnet,  as  at  the  right  of  the  cut,  A.  When  this  bonnet  is 
removed  the  exhaust  and  exhaust  closure  CH  can  be  observed.  These 

100 


THE  BUCKEYE   PISTON   VALVE 


101 


conditions  necessitated  the  system  of  marks  which  will  be  found  on  the 
valve  stems  with  letters  adjacent  thereto,,  the  meaning  of  which  letters  is 
as  follows : 


ON  CUT-OFF  VALVE  STEMS: 
CB,  cut-off,  bed  end. 
C,  center  of  travel. 
CH,  cut-off,  head  end. 


ON  MAIN  VALVE  STEMS: 
T  T,  ends  of  travel. 
LH,  lead,  head  end. 
CB,  compression,  bed  end. 
(7,  center  of  travel. 
CH,  compression,,  head  end. 
LB,  lead,  bed  end. 

To  USE  THE  MARKS 

Provide  a  parallel  straight-edge  of  thin  wood 
or  metal,  of  suitable  length,  and  exactly  2  ins. 
wide.  Eemove  the  packing  from  the  stuffing 
boxes  L,  M,  N,  and  shove  the  glands  home 
against  their  collars  and  bind  them  there  with 
followers.  Then  place  the  straight-edge  against 
the  projecting  end  of  the  gland  and  when  its 
outer  edge  cuts  any  of  the  marks  (except  T  T) 
the  event  indicated  by  it  should  be  just  taking 
place. 

Marks  T  T  do  not  indicate  events,  but  ex- 
tremes of  travel,  and  before  testing  by  any  of  the 
others  these  must  be  cut  by  the  straight-edge  at 
ends  of  travel.  If  such  is  found  not  to  be  the 
case,  the  adjustment  required  to  correct  will  be 
found  as  follows : 

SETTING  THE  MAIN  VALVE  AND  ECCENTRIC. 
— First,  test  and  correct  the  lengths  of  the  valve 
connections — the  eccentric  rod  and  short  connec- 
tion between  the  rocker  arm  and  valve  stem.  If 
the  eccentric  has  been  set  to  marks,  this  is 
done  by  equalizing  the  leads  and  compressions, 
particularly  the  compressions,  but  to  make 
our  instructions  cover  all  possible  cases  we 
will  suppose  that  the  eccentric  is  out  of  po- 
sition by  an  indefinite  and  unknown  amount. 

In  that  case,  the  only  test  of  the  proper  length  of  the  rods  is  equal- 
ity of  maximum  admission  openings,  which  once  equalized  will  remain 
so  in  all  positions  of  eccentric.  For  this  test  the  shaft  is  revolved 
to  each  extreme  of  the  eccentric's  travel  in  turn,  the  admission  opening 


FIG.    105B. 


102  VALVE   SETTING 

showing  in  each  case  (by  marks  on  the  valve,  remember)  measured  and 
compared  and  if  found  unequal,  the  length  of  the  connections  changed 
by  an  amount  equal  to  one  half  the  difference  between  the  two  openings, 
lengthening  or  shortening  as  required  so  as  to  throw  the  valve  toward 
the  end  at  which  the  smallest  opening  was  shown.  For  instance,  suppose 
the  smallest  opening  was  shown  at  the  "  crank  end,"  the  connections  should 
be  shortened,  and  vice  versa. 

But  instead  of  testing  by  equality  of  maximum  admission  openings  as 
here  stated,  test  by  the  marks. 

When  the  above  adjustment  is  correctly  made  all  subsequent  ones  must 
be  made  by  turning  the  eccentric  on  the  shaft,  the  length  of  the  valve  con- 
nections being  then  correct  under  all  circumstances. 

To  SET  ECCENTKIC  in  correct  angular  position,  place  crank  on  one  of 
its  dead  centers  and  turn  the  eccentric,  if  need  be,  till  the  mark  LH  or 
LB  is  cut  by  the  straight-edge,  according  as  the  piston  may  be  at  the 
"head"  or  "bed"  end  of  cylinder.  This  completes  the  set  of  the  main 
valve,  unless  subsequent  indicator  tests  should  show  the  desirability  of 
slight  changes  of  adjustment.  Thus  if  compression  shows  inequality,  it 
is  desirable  to  equalize  them,  though  in  doing  so  the  equalization  of  marks 
T  T  has  to  be  slightly  departed  from.  They  are  only  as  correct  as  they 
can  be  made  without  indicator  tests.  Equality  of  compressions  is  the  end 
to  be  attained,  though  that  is  more  a  matter  of  looks  on  the  diagram  than 
of  practical  running  qualities,  as  equalizing  by  the  marks  will  equalize 
compressions  accurately  enough  for  all  practical  purposes. 

WHEN  THE  MARKS  ON  THE  GUIDE  STEM  (as  at  the  right  end  of  the 
cut)  are  to  be  consulted,  the  bonnet  and  its  gasket  are  removed  and  the 
straight-edge  placed  against  the  face  of  the  chest  when  its  inner  edge  must 
cut  the  mark  to  be  consulted. 

Cut-off  adjustments  may  be  made  as  per  Part  I  of  this  chapter,  but  if 
there  is  no  steam  pressure  available  for  the  method,  the  cutting  of  mark 
CH  or  CB  by  the  outer  edge  of  straight-edge  will  give  the  same  indica- 
tion. Then  proceed  to  time  the  cut-off  in  piston  stroke,  bearing  in  mind, 
however,  that  when  a  condenser  is  in  use  the  governor  wheel  may  have  to 
be  advanced  to  properly  control  the  speed  when  running  as  lightly  loaded 
as  it  is  ever  likely  to  be. 

The  center  of  travel  mark  C  on  cut-off  stem  is  of  use  only  to  bring 
about  the  conditions  described,  Part  I,  but  in  a  different  and  simpler  way, 
thus :  when  the  mark  is  cut  by  the  straight-edge  as  directed  the  wrist  pins 
to  which  the  main  and  cut-off  valves  are  attached  should  be  about  in  line 
with  each  other. 


THE    POKTEK-ALLEN   ENGINE 

THIS  engine  is  of  the  four-valve  type,  and  the  special  feature  of  the 
gear  is  the  use  of  a  link,  actuated  by  a  single  eccentric  and  driving  inde- 
pendently the  steam  and  exhaust  valves. 

There  are  two  steam  valves  governing  the  admission  and  cut-off,  and 
two  exhaust  valves  governing  release  and  compression.  The  two  steam 
valves  are  placed  vertically  in  a  chest  at  one  side  of  the  cylinder,  and 
the  two  exhaust  valves  are  similarly  placed  in  a  second  chest  on  the  other 
side  of  the  cylinder,  as  shown  in  the  plan  of  Fig.  107.  All  the  valves 
are  driven  by  positive  gear,  and  their  movement  is  lengthwise  of  the 
cylinder. 

Figs.  108  and  109  are  respectively  horizontal  and  vertical  sections  of 
the  cylinder  and  valve  chests,  and  show  the  details  of  the  valves.  The 
valves  are  all  balanced  flat-side  valves,  working  between  the  valve  seat 
on  one  side  and  a  pressure  plate  on  the  other.  The  movement  of  each 
valve  covers  or  uncovers  four  openings  for  steam,  two  on  the  cylinder  face 
and  two  on  the  outer  face,  as  shown  by  the  arrows  in  Fig.  108;  so  that 
only  narrow  seats  and  short  valve  strokes  are  required  to  give  large  edge 
opening.  The  opening  movement  of  each  valve  is  inward  or  toward  the 
center  of  the  cylinder. 

The  arrangement  of  the  valve  gear  is  shown  by  the  elevation  and  plan 
of  Figs.  106  and  107,  and  the  link  detail  of  Fig.  110.  The  eccentric  E 
is  forged  on  the  shaft  and  is  coincident  with  the  crank.  The  eccentric 
strap  and  the  curved  link  L  are  made  in  one  piece,  as  shown,  and  the 
link  is  pivoted  at  its  central  point  on  the  trunnions  t,  which  in  turn  are 
pivoted  to  the  frame  at  the  fixed  point  A.  The  vibration  or  horizontal 
movement  of  the  trunnions  is  equal  to  the  throw  of  the  eccentric.  In 
the  slot  of  the  link  is  the  block  5,  from  which  are  driven  the  two  steam 
valves.  The  short  rock  shaft  s  on  the  frame  is  actuated  by  the  outer  arm 
a,  which  is  connected  by  the  steam  rod  with  the  block  in  the  link.  It 
carries  on  its  inner  end  the  two  arms  H  and  0  which  drive  respectively 
the  head-end  and  crank-end  steam  valves,  through  the  medium  of  the 
two  coupling  rods  li  and  c,  and  the  two  valve  stems.  The  steam  valves  are 
offset  in  the  chest,  as  shown  by  Fig.  106,  in  order  that  connection  to  each 

103 


104 


VALVE  SETTING 


valve  may  be  made  at  its  center  of  gravity;  and  short  guides  are  provided 
at  the  connections  of  the  levers  H  and  C  and  the  valve  stems. 

An  inspection  of  Fig.  110  will  show  that  the  link  has  a  peculiar  move- 
ment,  composed  of  the  horizontal  and  vertical  throws   of  the  eccentric. 


The  link  is  restrained  from  rising  by  the  trunnions,  and  the  horizontal 
throw  of  the  eccentric  draws  off  the  lap  of  the  valve,  while  the  vertical 
throw  tips  the  top  of  the  link  alternately  to  and  from  the  cylinder,  as 
the  eccentric  center  rises  or  falls  in  its  revolution,  the  upward  throw  tip- 


THE  PORTER-ALLEN  ENGINE 


105 


ping  the  link  toward  the  cylinder  and  the  downward  throw  tipping  it 
from  the  cylinder  or  toward  the  shaft.  This  tipping  of  the  link  opens 
and  closes  the  steam  valves  by  rocking  the  rock  shafts  by  means  of  the 
steam  rod  and  arm  a. 

This  movement  is  shown  by  Figs.  106,  107,  111,  and  112,  the  last 
two  being  in  diagram  and  exaggerated  for  clearness.  In  Figs.  106,  107, 
and  111  the  engine  is  on  the  head-end  center;  the  head-end  steam  valve 
is  open  for  lead,  and  the  crank-end  valve  is  closed,  the  eccentric,  the  link, 
and  the  arms  a,  H,  and  C  being  about  in  the  positions  shown.  In  Fig. 
112  the  engine  has  made  part  of  its  stroke  and  the  eccentric  has  reached 
the  position  shown.  The  upward  movement  of  the  eccentric  has  tipped 
the  link  toward  the  cylinder  and  the  block  is  back  of  its  former  position, 


FIG.    108.  —  HORIZONTAL   SECTION   OF   CYLINDER. 

as  shown  by  the  dotted  line  dropped  from  Fig.  111.  This  has  pushed 
arm  a  to  the  left,  and  has  pulled  the  head-end  valve  to  the  right  and 
wide  open  by  means  of  arm  H,  rod  h,  and  the  lower  connection.  As  the 
arm  H  is  nearly  in  its  upper  or  midposition,  the  slight  angular  move- 
ment of  the  rock  shaft  s  results  in  a  comparatively  large  horizontal  move- 
ment and  the  valve  is  opened  quickly.  At  the  same  time  the  arm  C  moved 
downward  through  the  same  arc  as  arms  a  and  H,  pulling  the  crank- 
end  valve  to  the  right;  but,  as  arm  C  is  about  at  the  end  of  its  travel, 
the  angular  movement  results  in  only  a  very  small  horizontal  movement, 
hardly  moving  the  crank-end  valve  on  its  seat.  Thus  the  valves  are 
opened  and  closed  quickly  by  the  middle  movement  of  their  arms,  and 
have  very  little  movement  while  open  or  closed,  as  the  arms  are  then  at 
the  extremes  of  the  travel.  As  shown  by  Fig.  106,  the  position  of  the 
block  in  the  link  is  under  the  control  of  the  governor,  a  dropping  of 
speed  causing  the  governor  balls  to  drop  and  so  raise  the  block,  and  an 


106 


VALVE   SETTING 


increase  of  speed  forcing  the  block  down  toward  the  trunnions.  When  the 
block  is  at  the  top  of  the  link,  as  in  Fig.  110,  the  steam  rod  receives  the 
full  tipping  motion  of  the  link  and  cut-off  takes  place  at  the  maximum 
point,  about  six  tenths  of  the  stroke.  On  the  other  hand,  when  the  gover- 
nor balls  are  in  the  extreme  upper  position  the  block  is  forced  clear  down 
to  the  trunnions,  and  so  receives  none  of  the  tipping  motion  of  the  link. 
Then  the  valve  is  merely  opened  for  lead,  and  is  closed  immediately. 

Thus  the  steam  valves  are  always  opened  and  closed  quickly  at  the 
midtravel  of  their  arms;  the  velocity  of  cut-off  increases  as  the  cut-off 
is  lengthened,  since  the  block  is  higher  in  the  link,  and  so  corresponds 
to  the  increased  piston  velocity  near  midstroke;  and  the  velocity  of  valve 
movement  is  increased  directly  with  the  speed  of  the  engine. 

The  well-known  Porter  fly-ball  governor  is  used.  It  is  carried  on  a 
bracket  from  the  engine  frame  and  is  belted  to  the  crank  shaft.  Its  dis- 


FIG.    109. —  SECTION  AT   A-B,   LOOKING  TOWARD  CRANK. 

tinguishing  features  are  light  fly-balls  with  a  high  rotative  speed,  to  scruro 
sensitiveness,  and  a  heavy  ball  or  weight  on  the  vertical  shaft  to  secure 
the  gravity  effect  required  to  keep  the  revolving  balls  in  their  effective 
plane.  Its  sole  function  is  to  raise  or  lower  block  B  in  the  link.  Since 
the  valves  are  light,  perfectly  balanced,  have  a  central  draft  or  attach- 
ment, and  small  movement,  very  little  force  is  required  to  move  them  and 
the  load  on  the  governor  is  small. 

The  exhaust  valves  are  placed  in  a  separate  chest  on  the  crank  sido 
of  the  cylinder,  opposite  the  steam  valves.  They  have  a  fixed  travel  and 
are  driven  from  a  stationary  point  on  the  link  by  means  of  the  exhaust 
rod,  the  rock  shaft  e,  which  passes  through  the  engine  frame,  and  the  two 
arms  E  and  F  on  the  opposite  ends  of  shaft  e,  as  shown  in  Figs.  106  and 
107.  They  are  so  arranged  that  the  opening  movement  of  one  valve  and 
the  closing  movement  of  the  other  takes  place  at  the  middle  of  the  vibra- 
tion of  the  arms  where  the  motion  is  swiftest. 


THE  PORTER-ALLEN   ENGINE 


107 


One  half  of  the  exhaust  valve  movement  is  sufficient  to  give  full  port 
area  for  release,  and  this  is  accomplished  by  the  time  the  piston  has  com- 
pleted its  forward  stroke;  so  that  the  return  stroke  is  begun  with  a  wide 
open  release  port  in  front  of  the  piston.  Closing  does  not  begin  until 
the  piston  has  accomplished  more  than  half  stroke,  where  its  speed  is 
diminishing,  so  that  there  is  no  throttling  of  the  exhaust  until  just  after 
port  closure. 

The  details  of  the  cylinder  valves  and  pressure  plates  are  shown  in 
Figs.  108  and  109,  the  latter  being  a  section  through  the  head-end  valves, 


FIG.    110. —DETAIL    OF   LINK. 

and  showing  the  steam  valve  on  this  end  lower  than  on  the  other,  as  is 
also  shown  in  dotted  lines  on  Fig.  106.  The  valves  consist  simply  of  flat 
rectangular  frames  with  a  central  bar  for  the  attachment  of  the  valve 
stem. 

The  pressure  plates  of  the  steam  valves  are  held  between  the  side 
guides  g  g,  Figs.  108  and  109 ;  and  in  the  other  direction  between  a 
planed  spot  on  the  cover  and  the  valve  seat.  Steep  beveled  seats  are  on 
the  valve  seats  as  shown,  and  the  pressure  plate  is  held  in  position  by  the 
adjusting  screws  or  bolts  &,  Fig.  109. 

The  plates  are  adjusted  by  these  bolts;  screwing  the  bolts  in  forces 
the  plate  up  and  away  from  the  valve;  backing  the  bolts  out  lowers  the 
plate  and  the  steam  pressure  holds  it  against  the  valve.  They  are  properly 
adjusted  when,  with  steam  on  and  all  parts  at  the  working  temperature, 
the  valves  may  be  moved  easily  by  the  starting  bar  without  leaking  at  the 
joints  or  seats.  These  plates  are  made  hollow,  as  shown,  to  admit  steam  to 


108  VALVE  SETTING 

the  outer  edges  of  the  valves.  The  adjusting  bolt  has  a  hardened  steel  end 
which  works  on  a  hard-steel  nut  or  socket  in  the  pressure  plate.  The 
exhaust  valves  are  also  flat  rectangular  frames  and  are  set  lower  than 
the  bottom  of  the  cylinder,  in  order  to  secure  perfect  drainage. 

The  pressure  plates  for  these  exhaust  valves  are  shown  at  the  left  in 
Fig.  109.  They  are  not  adjustable,  as  are  those  for  the  steam  valves,  but 
are  bolted  to  the  face  of  the  valve  seat.  They  are  also  made  hollow  to 
furnish  ample  exhaust  passage. 

All  four  plates  are  made  very  stiff  and  rigid  to  prevent  them  from 
springing  and  leaking  when  subjected  to  the  pressure. 

A  removable  cover  over  each  valve  affords  ready  access  to  valve,  pres- 
sure plate,  and  seat. 

In  short,  the  distinguishing  features  of  this  valve  gear  are  flat-balanced 
valves  at  four  points  of  the  cylinder,  the  steam  valves  at  one  side  and 
the  exhaust  valves  at  the  other;  all  valves  independently  adjustable;  a 
single  eccentric  with  link  motion  and  positive  gear  for  all  valves,  with  a 
fly-ball  governor  controlling  the  cut-off;  an  arrangement  of  gear  whereby 
the  valve  motion  is  made  to  agree  in  velocity  with  that  of  the  piston, 
and  an  ability  to  run  at  any  speed,  due  to  the  use  of  positive  gear. 

SETTING  THE  VALVES 

The  joint  of  the  valve  gear  consists  of  hardened  steel  pins  and  hard- 
ened steel  bushings  in  the  rod  ends;  there  is  therefore  no  adjustment  in 
the  length  of  the  rods  and  the  valve  strokes  are  determined  and  fixed 
when  the  engine  is  built,  requiring  no  adjustment. 

To  set  the  steam  valves,  first  place  the  engine  on  the  head-end  center 
in  the  usual  manner,  taking  up  all  lost  motion  in  the  direction  of  rota- 
tion. Block  the  governor  up  until  the  block  B  comes  down  to  the  center 
of  the  trunnions.  Then  remove  the  valve  covers  and  set  the  head-end  valve, 
by  means  of  the  valve  stem,  until  it  shows  the  proper  lead — ^  in.  or  more 
— at  that  end,  as  given  by  the  engine  builder.  Then  turn  the  engine  to 
the  other  center  and  set  the  crank-end  valve  to  show  the  same  lead.  Now 
let  the  governor  down,  bringing  the  block  to  the  top  of  the  link.  This 
will  move  the  valve  a  short  distance  toward  the  crank,  no  matter  which 
center  the  engine  is  on.  This  increases  the  lead  at  the  head  end  and 
decreases  it  at  the  crank  end,  so  that  the  lead  at  the  two  ends  is  varied 
according  to  the  position  of  the  block  or  the  distance  to  which  steam  is 
carried.  By  varying  the  lead,  the  points  of  cut-off  are  equalized,  and  the 
correctness  of  the  valve  setting  may  be  tested  by  blocking  the  governor 
in  any  position  whatever,  and  turning  the  engine  over  throughout  a  com- 
plete revolution.  The  points  of  cut-off  or  the  distance  the  piston  lias  trav- 
eled when  cut-off  takes  place  will  be  the  same  for  both  forward  and  return 


THE   PORTER-ALLEN   ENGINE 


109 


110  VALVE   SETTING 

strokes.  This  may  be  demonstrated  by  marking  both  crosshead  and  guide 
at  cut-off  on  the  forward  stroke,  and  making  a  second  cut-off  mark  on  the 
guide  the  same  distance  from  the  dead  center  on  the  return  stroke.  When 
the  crosshead  reaches  this  second  mark,  on  the  return  stroke,  the  valve 
should  just  close  the  port. 

It  will  be  seen  that  the  position  of  the  trunnions,  or,  in  other  words, 
their  vertical  adjustment,  is  an  important  matter.  To  provide  for  accu- 
rate adjustment  and  to  allow  for  wear  of  the  shaft  or  other  bearing,  the 
pin  on  which  these  trunnions  are  pivoted  is  adjustable  by  the  wedge  k 
and  bolt  8,  shown  in  Fig.  110.  If  the  trunnions  are  not  in  line  with  the 
center  line  of  the  eccentric,  the  travel  of  both  steam  and  exhaust  valves 
will  be  affected  and  inequalities  in  all  the  functions  will  result. 

Further  adjustments,  shown  by  the  indicator  to  be  necessary,  may  be 
made  by  lengthening  or  shortening  the  valve  stem  at  the  socket  near  the 
guide  shown  in  Fig.  106.  The  chest  need  not  be  opened.  The  exhaust  valve 
motion  is  imparted  by  nonadjustable  links  and  rocker  arms;  all  that  is 
necessary  is  to  measure  out  on  the  guides,  from  each  dead  center,  a  dis- 
tance equal  to  the  point  of  compression.  Then  place  the  engine  on  the 
forward  stroke  to  such  a  position  that  the  mark  on  the  crosshead  coincides 
with  this  point  of  compression;  then,  by  means  of  the  valve  stem,  set  the 
crank-end  exhaust  valve  line  and  line  with  its  port.  Turn  the  engine 
over  until  the  crosshead  mark  agrees  with  the  compression  mark  on  the 
return  stroke  and  set  the  head-end  exhaust  valve  line  and  line.  The  dis- 
tance of  the  point  of  compression  from  the  beginning  of  the  stroke  may 
be  obtained  from  the  engine  builder,  as  may  also  the  lead.  When  these 
are  not  known,  adjustments  in  the  proper  direction  must  be  made  from 
a  series  of  indicator  diagrams,  continuing  the  adjustments  until  the  dia- 
grams show  the  proper  outlines. 

Each  valve  is  held  between  two  pairs  of  nuts,  the  inner  ones  of  which 
are  flanged.  When  the  valve  is  properly  set,  screw  the  inner  nuts  up  to 
the  valve  just  enough  to  take  up  lost  motion  without  pinching  the  valve, 
and  set  up  the  outer  or  lock  nuts  tightly  against  the  inner  ones. 

Before  replacing  the  chest  covers  after  making  adjustments,  it  is  well 
to  turn  the  engine  slowly  throughout  an  entire  revolution,  with  the  gov- 
ernor blocked  up  to  the  running  position,  and  see  that  lead,  cut-ofT,  n-lciiso. 
and  compression  take  place  correctly  and  that  all  parts  move  free  and 
clear.  A  further  trial  with  the  governor  clear  up  should  show  no  steam 
opening  except  for  lead. 


XI 
THE    FITCHBURG    ENGINE 

THE  most  distinctive  feature  of  the  Fitchburg  steam  engine  is  the  valve 
motion,  valve  and  governor  design  being  next  in  importance.  Although 
the  designers  and  builders  of  these  engines  advocate  moderate  piston  and 
fly-wheel  speeds,  the  valve  motion  and  governor  are  adaptable  to  all  high 
speeds  required  of  reciprocating  engines.  The  number  of  this  type  of 
engine  in  use  makes  a  study  of  its  distinctive  features  worth  the  operating 
engineer's  while. 

The  general  arrangement  of  the  valve  gear  is  shown  in  Fig.  113.  The 
steam  valves  act  separately,  being  operated  by  the  governor  eccentric  by 
means  of  the  rods  A  and  B  and  the  cranks  C  and  D  driving  the  cams  by 
means  of  wrist  cranks  on  the  opposite  ends  of  their  shafts.  The  exhaust 
valves  are  on  one  stem  actuated  by  a  fixed  eccentric  on  the  engine  shaft 
through  the  medium  of  the  rods  E  and  F.  It  will  be  noted  that  the  exhaust 
eccentric  and  valve  rods  are  so  located  that  the  movement  of  the  eccentric 
is  transmitted  directly  to  the  valve. 

Both  steam  and  exhaust  valves  are  adjustable  to  wear.  The  adjust- 
ment will  be  understood  by  reference  to  Fig.  114,  which  shows  the  details 
of  one  of  the  steam  valves.  A  lengthwise  section  of  the  valve  and  the  valve 
chest  is  shown  in  the  lower  figure,  and  the  valve  is  shown  removed  at  J, 
while  a  cross  sectional  view  of  the  outer  shell  with  tongue  and  inner  cone 
is  shown  in  the  upper  right-hand  corner. 

The  construction  of  the  valve,  as  shown  in  the  lower  view,  consists  of 
the  valve  stem  A,  on  which  the  valve  parts  are  kept  in  place  by  the  nuts 
B.  The  follower  rings  C  and  D  fit  into  and  bind  in  place  the  taper  cone 
E  E,  which  is  used  to  set  out  the-  expansible  ring  F  F.  Adjustment  bolts 
G  G  are  used  in  connection  with  adjusting  the  valve  to  wear. 

To  adjust  the  valve,  first  slacken  the  nuts  B  just  enough  to  allow  the 
ring  F  to  expand  slightly,  then  to  expand  it  slacken  the  bolts  G  G 
and  run  the  set  screws  H  in  until  the  required  expansion  is  accomplished. 
If  the  first  trial  is  not  sufficient,  continue  until  the  proper  adjustment  is 
reached.  If  it  is  too  tight,  reverse  the  process  by  first  slackening  the  set 
screws  H  and  tightening  the  bolts  G.  While  setting  up  or  slackening  the 
adjustment,  keep  trying  the  valve  by  rocking  it  back  and  forth  with  the 

111 


UJ 


CD 


O 


THE  FITCHBURG  ENGINE 


113 


starting  bar.     After  the  adjustment  is  completed  tighten  the  nuts  B  and 
then  see  that  the  screws  and  bolts  G  and  H  are  tight  and  evenly  set  up  all 


\ 


Sectional  View  of  Packing  Rings 


FIG.  114.  — LENGTHWISE  SECTION  OF  STEAM  VALVE,  ALSO  THE  VALVE  REMOVED, 
AND  A  SECTION  SHOWING  TONGUE. 

around.     This  method  of  adjustment  applies  to  both  steam  and  exhaust 
valves. 

THE  SEPARATE  STEAM  AND  EXHAUST  VALVES 

The  separate  steam  and  exhaust  valves  are  shown  in  Fig.  115.  The 
exhaust  valve  A  is  not  usually  ported  while  the  steam  valve  B  is  double- 
ported  and  balanced,  as  shown  in  Fig.  114.  In  Fig,  115  the  valve  motion 


114 


VALVE   SETTING 


is  shown  in  the  center  of  its  travel,  with 
the  valves  lapped.  While  in  this  position 
the  rocker  arms  C  and  D  and  cranks  E  and 
F  should  be  vertical,  or  at  exact  right  an- 
gles with  the  center  line  of  the  engine,  with 
the  cams  G  and  H  as  shown  and  the  valvo 
rod  so  adjusted,  that  the  valves  have  their 
proper  lap.  When  all  the  rods  are  properly 
adjusted  as  to  length  the  rocker  arms  and 
cranks  will  travel  an  equal  distance  on  each 
side  of  the  center  line  on  which  they  rest 
in  this  cut.  The  nut  J  on  the  steam  reach 
rod  has  a  right-and-left  thread  in  it  and  by 
loosening  the  lock  nuts  and  turning  the 
center,  the  length  of  this  rod  can  be  altered 
to  bring  the  cranks  in  line. 

In  Fig.  114  the  steam  valve  is  shown 
in  the  position  where  it  is  just  opening  (the 
arrows  denoting  the  direction  of  the  flow 
of  steam).  Fig.  116  shows  the  same  vul\v 
opening;  note  the  position  of  the  cranks 
here.  They  are  both  at  a  middle  position 
of  travel  in  one  direction.  The  governor 
eccentric  is  now  at  middle  throw.  One 
steam  valve  is  opening  and  the  other  one  is 
closed.  When  the  positions  are  reversed 
and  the  eccentric  is  on  the  other  center,  the 
steam  valve  here  shown  open  will  be  back 
in  the  position  shown  in  Fig.  115,  while 
the  crank-end  valve  will  be  open. 

The  exhaust  valves  are  to  be  evened  up 
on  their  rods  and  their  eccentric  so  set 
that  they  close  and  open  alternately  at 
about  seven  eighths  of  the  engine  stroke. 

It  will  be  noted  that  the  extreme  steam- 
valve  travel  is  equal  to  the  steam  lap  and 
nearly  the  width  of  main  port  (Fig.  115). 
The  steam  valve  is  given  this  travel  through 
the  medium  of  the  cams,  and  herein  lies  the 
peculiarity  of  this  valve  motion. 

The  largest  part  of  the  cam  slot  is  of 
the  same  radius  as  the  circle  that  the  driv- 
ing pin  and  roll  on  the  wrist  crank  pass 


THE   FTTCHBURG   ENGINE 


115 


through,  so  that  when  the  pin  is  moving  down  and  away  from  the  steam 
chest  and  back  again  to  the  position  shown  in  Fig.  115.,  the  valve  is  at  rest. 
This  is  for  a  period  of  one  half  the  engine  revolution.  To  prevent  a  too 
sudden  action  of  the  valve,  the  slot  is  just  enough'  off  from  the  point  M  to 
the  end  to  start  the  cam  and  valve  in  motion  slightly  before  the  valve  opens. 


STEAM  VALVE  is  BALANCED 

As  can  be  seen,  the  steam  valve  is  balanced  by  having  the  steam  pressure 
on  all  sides,  with  the  exception  of  the  amount  of  the  area  of  the  valve 
stem  on  the  one  end. 

This  exception  acts  as  an  assistant  in  obtaining  quick  cut-off  for  the 
pressure  on  the  outside  end  of  the  valve  is  just  enough  more  than  that  on 


FIG.    116. 

the  other  end  to  force  the  valve  back  without  the  aid  of  the  cam  motion 
when  the  return  begins.  This  is  evidenced  by  the  fact  that  when  steam 
pressure  is  on  the  cam  is  kept  pressed  against  the  driving  roll  at  all  times 
and  after  long  use  there  is  no  sign  of  wear  on  the  back  side  of  the  slot. 

The  steam  valve  admits,  and  the  exhaust  valve  releases,  steam  over 
the  inside  ends.  The  steam-valve  motion  is  indirect,  on  account  of  the 
cranks,  and  the  exhaust  motion  is  direct.  With  one  eccentric  the  exhaust 
valves  would  necessarily  have  to  release  over  the  outside  ends,  but  as  the 
eccentrics  are  separate  the  exhaust  release  is  as  stated.  For  this  reason  the 
governor  and  exhaust  eccentrics  both  lead  the  cranks. 

Fig.  117  shows  the  relative  position  of  the  crank  pin  and  steam  eccentric 


no 


VALVE   SETTING 


at  about  the  point  A  on  the  dotted  line  R  A,  or  it  is  about  90  degrees  plus 
37  degrees  for  lap  and  lead  ahead  of  the  crank,  and  the  exhaust  eccentric 
is  approximately  at  90  degrees  ahead  of  the  crank.  This  latter  fact  may 
be  useful  to  know  in  the  event  of  a  slipped  eccentric  and  the  minimum 
time  for  adjustment. 

Fig.  115  shows  both  eccentrics  at  90  degrees,  while  Fig.  116  shows  the 
lead  of  the  steam  valve  distorted,  for  clearness  of  illustration,  but  the 
valve  crank  is  in  the  same  position  as  when  the  crank  pin  is  a  little  by  the 

center    and    the    eccentric    is    ad- 


FIG.    117. 


is 

vanced  a  little  beyond  the  point 
shown  in  Fig.  117.  When  in  this 
position  the  steam  is  cut  off  at 
about  one-fifth  stroke  or  in  full 
travel  about  three-fourths  stroke. 
The  angle  of  advance  increases  as 
the  eccentric  is  thrown  across  the 
shaft  by  the  action  of  the  governor 
as  speed  tends  to  increase,  thus 
accomplishing  the  regulation  of 
speed.  For  a  full  understanding 
of  this  action  refer  to  Fig.  117. 
The  action  is  as  follows:  As  long 
as  the  engine  is  below  speed,  the 
eccentric  is  kept  in  its  longest 
throw  by  the  tension  of  the 

springs  and  steam  follows  about  three  fourths  of  the  stroke,  but  as 
soon  as  the  proper  speed  is  reached  centrifugal  action  causes  the  weights 
II  to  overcome  the  tension  of  the  springs  and  to  move  outward,  at 
the  same  time  lengthening  the  springs;  by  means  of  the  connecting 
rods  G  G  the  outward  motion  of  the  weights  turns  the  suspension  arms 
C  upon  their  fulcra  and  through  the  ears  B  the  eccentric  is  carried 
across  the  shaft  from  8  toward  R,  and  as  the  arcs  described  by  the  centers 
B  B  are  in  opposite  curves  they  compensate  each  other,  and  the  center 
8  of  the  eccentric  follows  a  straight  line  in  its  movement,  preserving  a 
constant  lead  opening  or  otherwise  as  desired.  This  manifestly  decreases 
the  eccentricity,  and  increases  the  advance  of  the  eccentric,  giving  an  earlier 
cut-off  to  the  valve  until,  when  the  eccentric  is  swung  squarely  back  of  the 
crank,  the  valve  opens  only  the  lead,  there  being  all  points  between  this  and 
extreme  cut-off  for  variation.  Upon  the  least  diminution  of  speed  the 
springs  have  more  power  than  the  centrifugal  force  of  the  weights,  and  the 
motion  of  the  parts  is  arrested  and  turned  in  the  opposite  direction,  giving 
a  later  cut-off,  as  more  work  is  performed  by  the  engine. 


THE  FITCHBURG  ENGINE  117 

How  TO  SET  AND  ADJUST  THE  VALVES 

Having  now  discussed  the  motion,  the  idea  is  to  get  a  working  knowl- 
edge of  how  to  set  the  valves  and  adjust  them  and  the  governor  for  various 
conditions. 

The  builders  give  the  erecting  men  a  set  of  instructions  for  their  guid- 
ance when  first  setting  up  the  engine,  extracts  of  which,  given  herewith, 
should  with  the  foregoing  afford  a  working  knowledge  of  the  adjustment 
of  these  engines,  under  any  conditions,  to  the  operator. 

The  location  of  the  governor  case  is  determined  by  placing  the  engine 
on  one  dead  center  and  rolling  the  case  around  the  shaft  until  the  offset 
of  the  eccentric  is  on  the  opposite  side  of  the  shaft  from  the  crank  pin. 
Then  roll  carefully  into  such  position  that  when  (with  the  springs  re- 


FIG.   118. 

moved)  the  eccentric  is  thrown  back  and  forth  across  the  shaft,  no  end 
motion  is  given  the  valve  rod.  At  this  place  tighten  the  governor  case 
firmly  upon  the  shaft  and  roll  the  shaft  to  the  opposite  dead  center  and 
again  move  the  eccentric  back  and  forth  across  the  shaft,  and  if  there  is  at 
this  end  any  end  motion  to  the  valve  rod  change  the  position  of  the  gov- 
ernor case  on  the  shaft  enough  to  make  the  motion  just  half  as  much,  then 
fasten  the  governor  case  firmly  in  this  final  position  by  drilling  into  the 
shaft  for  the  point  of  the  set  screw  and  then  tightening  the  clamp  bolts 
to  place  solidly.  Put  in  the  springs  and  tighten  them  until  the  proper 
number  of  revolutions  is  obtained,  being  sure  to  tighten  up  the  springs  that 
go  through  the  counterbalance  which  hangs  nearest  the  springs  (when  the 
governor  is  at  rest)  about  three  fourths  of  an  inch  more  than  the  springs 
on  the  other  side. 

The  travel  of  the  exhaust  valves  can  first  be  evened  up,  before  their 
eccentric  is  tightened  upon  the  shaft,  by  rolling  the  eccentric  around  the 
shaft  to  its  extreme  throw  at  each  end.  It  should  then  be  set  so  that  the 


118 


VALVE   SETTING 


port  is  just  closed  when  the  crosshead  has  traveled  a  little  less  than  seven 
eighths  of  its  stroke,  and  the  set  screw  firmly  screwed  upon  the  shaft. 

To  adjust  the  steam  valves,  place  the  latch  of  the  hook  in  the  center 
of  the  half  spiral  slot  and  clamp  the  hook  firmly  by  its  lever,  evening  up 


FIG.    119. 

the  movement  of  the  wrist  cranks  by  the  right  and  left  nuts  in  the  valve 
rod,  so  that  in  a  revolution  of  the  engine  shaft  they  rock  evenly  each  side 
of  a  vertical  line  drawn  from  centers  of  their  shafts;  set  the  engine  ex- 
actly on  the  head  center  and  move  the  small  valve  rod  attached  to  the 
head  valve  in  or  out  of  its  cam  until  the  port  is  opened  the  proper  lead 
(in  usual  cases  -fa  of  an  inch),  and  tighten  the  set  screw  in  the  neck 
of  the  cam  upon  the  rod  firmly.  Roll  the  engine  to  opposite  center  and 


FIG.  120. 


set  the  other  valve  in  the  same  way.  After  the  valves  are  thus  set  as 
closely  as  possible  they  should,  if  practicable,  be  adjusted  by  use  of  the 
indicator  when  the  engine  is  under  partial  or  full  load,  as  no  mere  meas- 
urements can  ever  set  the  valves  exactly  right  in  any  engine.  The  exhaust 
valves  of  the  low-pressure  cylinder  can  be  set  the  same  as  for  the  high- 
pressure  cylinder. 


THE  FITCHBURG  ENGINE  119 

The  shaft  governor  depends  for  its  action  upon  the  centrifugal  power 
of  the  two  weights  nearest  the  rim.,  which,  through  the  connecting  rods, 
move  the  counterbalancing  weights  to  which  the  eccentric  is  attached  and 
thus  carry  the  eccentric  across  the  shaft,  altering  the  throw  of  the  valve 
rod  and  the  point  of  closure  of  the  admission  valves.  The  centrifugal 
power  of  the  weight  arms  is  exerted  against  the  springs,  and  as  the  point 
of  cut-off  is  earlier  the  more  the  weight  arms  are  thrown  out  toward  the 
rim  it  follows  that  to  increase  the  speed  of  the  engine,  the  springs  must  be 
tightened  or  the  weight  reduced;  and  to  decrease  the  speed,  the  springs 
must  be  loosened  or  the  weight  increased.  The  springs  should  not  be 
stretched  much  over  1J  times  the  length  of  the  coil  when  unstretched.  The 
engine  can  be  changed  several  revolutions  by  adjusting  the  tension  of  the 


FIG.  121. 

springs,  but  if  a  marked  change  is  desired,  confer  with  the  builders  and 
they  will  direct  what  should  be  done.  Care  should  be  taken  that  a  little 
even  friction  be  maintained  between  the  face  of  the  eccentric  and  the  gov- 
ernor case  to  prevent  dancing,  and  this  is  secured  by  the  springs  and  wash- 
ers on  the  ends  of  the  pins  which  carry  the  counterbalance  weights.  Once 
adjusted  they  are  right  for  a  long  time. 

Adding  to  the  centrifugal  weight  arms  and  increasing  the  tension  of 
the  springs  make  the  governor  more  sensitive.  Do  not  make  radical 
changes  in  the  weights  or  springs  of  the  governor  without  consulting  with 
the  builders. 

PRACTICAL  ILLUSTRATION  OF  SETTING  VALVES 

An  illustration  of  valve  setting  on  this  type  of  engine  is  given  in 
the  following  experience.  On  indicating  the  engine  a  friction-load  dia- 
gram such  as  is  shown  in  Fig.  118  was  taken.  The  head-end  diagram 
showed  some  30  Ibs.  less  initial  pressure  than  on  the  crank  end,  the  lead 
was  late  and  the  cut-off  early.  To  even  up  the  initial  pressure  on  the 
two  ends,  the  reach  rod  to  the  wrist  cranks  was  shortened  by  turning 


120 


VALVE  SETTING 


the  nut  J,  Fig.  115.  This  had  the  effect  of  more  lap  on  the  head-end 
steam  valve  and  less  on  the  crank  end,  giving  the  diagram  in  Fig.  119, 
where  the  initial  pressures  were  brought  within  8  Ibs.  of  each  other 

by  the  change.  It  will  be  noted  that  the 
head  end  had  the  latest  cut-off  by  the  change. 
Before  making  further  changes,  the  diagram 
Fig.  120  was  taken  with  about  one-third  load 
on  the  engine.  Under  these  conditions  the 
initial  pressure  is  about  equal,  with  the  cut-off 
still  late  on  the  head  end. 

The  valve  stems  enter  the  cams  a  straight 
fit  and  are  secured  by  a  set  screw.  The  crank-end  valve  stem  was  loosened 
up  in  the  cam  and  set  out  a  trifle  to  give  the  effect  of  less  lap.  The  dia- 
gram Fig.  121  was  then  taken  under  the  same  conditions  as  Fig.  120  and 
shows  the  cut-offs  to  be  about  even. 

In  conclusion  it  may  be  well  to  mention  that  in  keying  up  any  of 
the  pin  bearings  of  this  engine  a  wedge  adjustment 
is  used.  On  both  ends  of  the  connecting  rod  is  a 
box,  shown  in  detail  in  Fig.  122.  To  set  up  on 
these  boxes,  loosen  the  bolt  B  and  tighten  A.  A  good 
way  to  work  this  adjustment  is  to  slacken  B  to  a 
considerable  extent,  then  with  the  flat  side  of  the 
wrench  tap  it  down  lightly  until  it  seems  tight,  then 
take  up  the  slack  on  the  bolt  A  just  enough  to  know 
you  have  it  set  up,  then  screw  B  down  into  place,  set- 
ting it  up  tight. 

The  arrow  marked  on  the  outside  end  of  every 
bo:J  connection  denotes  the  direction  the  wedge  should 
be  moved  to  take  up  lost  motion.  To  slacken,  reverse 
the  above  operation.  Fig.  123  shows  the  crosshead  of 
these  engines  where  the  adjustment  of  the  shoes  is  the 
same.  On  the  end  of  the  gibs  arrows  are  stamped, 
vhich  also  denote  the  direction  to  key  up  the  wedge.  FIG.  123. 


XII 


THE    FLEMING   PISTON-VALVE    ENGINES* 

To  set  the  valves  of  a  Fleming  piston-valve  engine,  it  is  necessary  in 
the  first  place  to  get  reference  marks  on  the  fly  wheel  corresponding  to  the 
dead-center  positions  of  the  piston.  The  method  of  obtaining  these  has 
been  so  frequently  described  that  it  seems  almost  unnecessary  to  repeat  it 
here.  We  will,  however,  give  the  method,  since  it  constitutes  a  part  of  the 
operation  of  the  valve  setting. 

Turn  the  engine  in  the  direction  it  runs  until  the  piston  is  within,  say, 
an  inch  of  the  end  of  the  stroke ;  tram  the  fly  wheel  from  some  fixed  point, 


FIG.  124. 

such  as  the  subbase  extension,  and  make  a  center-punch  mark  at  each  end 
of  the  tram,  as  at  A  and  #,  Fig.  124.  Now  make  a  mark  on  the  edge  of 
the  lower  crosshead  shoe  and  one  exactly  in  line  with  it  on  the  lower 
guide;  then  turn  the  engine  in  the  direction  it  runs  until  these  two  marks 
coincide  again.  Train  the  wheel  again  from  the  same  point,  B,  on  the 
extension,  making  a  center-punch  mark  on  the  rim.  Now  find  a  point 
midway  between  the  marks  on  the  wheel  with  a  pair  of  dividers.  Turn 

*  Contributed  to  Power,  by  Thomas  Hall. 
121 


122 


VALVE   SETTING 


Exhaust  Edge Steam  .Edge. 


Crank  End 


Exhann  Edge 


End  Head 


FIG.   125. 


the  engine  over  until  the  tram  just  reaches  this  central  point  on  the  fly- 
wheel rim,  and  you  will  have  the  dead-center  position  of  the  crank  for 
that  end  of  the  stroke.  Use  the  same  method  to  find  the  other  dead  center. 
After  the  centers  have  been  located,  remove  the  valve  from  the  steam 
chest  or  valve  chamber,  and  make  an  accurate  templet  of  the  "  head  end  " 

and  "  crank  end."  Such  a  templet 
is  shown  by  Fig.  125.  Also  make  a 
correct  templet  of  the  valve  seat,  in 
the  valve  chamber,  making  one  end 
of  the  templet  even  with  the  face  of 
the  valve  chamber,  Fig.  126.  Mark 
the  ports,  head  end  and  crank  end, 
showing  both  edges  of  both  ports 
and  the  face  of  the  valve  chamber,  as 
Face  of  shown  by  Fig.  127,  where  E  repre- 

vaive  chamber          sents  the  exhaust  edges,  and  8  the 
steam  edges. 

These  templets  can  be  made 
from  any  light  material,  such  as 
sheet  zinc,  sheet  tin,  thin  strong 
pasteboard,  or  thin  wood  strips,  but 

the  edges,  if  made  of  wood,  to  insure  accuracy,  should  be  made  of  knife- 
edge  form. 

After  the  templets  have  been  made,  the  valve  can  be  placed  back  in  the 
valve  chamber  and  connected  up,  locating  approximately.  Now  turn  the 
engine  on  one  of  the  dead  centers  and  proceed  to  adjust  accurately. 

Fig.  128  shows  the  governor  wheel  on  the  crank-end  and  center  position 
for  a  right-hand  engine  running  over,  the  broken  horizontal  line  through 
the  center  being  the  center  line  of  the  engine.  The  governor  is  shown  in 
its  position  of  minimum  travel  by  the  dotted  lines,  and  of  maximum  travel 
by  the  full  lines.  Block  the  governor  in  its  minimum  position,  turn  the 
engine  onto  the  crank-end  center,  take  measurement  from  the  end  of  the 
valve  to  the  face  of  the  cylinder,  as  shown  by  Fig.  129,  and  transfer  this 
measurement  to  the  templets,  as  shown  by  Fig.  130,  when  the  amount  of 


FIG.  126. 


Crank  End  Port 


Head  End  Port       Face  of 

Valve  Chamber 


FIG.  127. 


lead  for  the  crank  end  can  be  readily  seen  and  measured  from  the  templets. 
The  amount  of  lead  will  vary  with  the  size  of  the  engine  and  the  steam 
pressure  used,  from  ^  to  J  of  an  inch  on  the  head  end,  and  practically 
double  this  amount  on  the  crank  end  for  noncondensing  engines. 


THE  FLEMING  PISTON-VALVE   ENGINES 


123 


On  condensing  engines  with  the  governor  in  this  position  and  the  crank 
on  the  head-end  center,  the  valve  will  have  from  ^V  to  TV  of  an  inch  lap, 
or  negative  lead,  according  to  the  size  of  the  engine  and  the  steam  pres- 
sure used,  and  should  be  about  line  and  line  on  the  crank-head  center. 
The  lead  increases  considerably  as  the  point  of  cut-off  increases. 

Upon  turning  the  engine  over  in  the  direction  in  which  it  runs,  with 
the  governor  in  its  minimum  travel  position,  until  the  greatest  movement 


FIG.  128. 

of  the  valve  is  obtained,  the  opening  must  not  be  sufficient  to  cause  the 
engine  to  run  away  when  the  load  is  thrown  off;  i.e.,  it  should  be  more 
than  sufficient  to  overcome  the  friction  of  the  engine.  In  order  to  insure 
this,  the  lead  or  port  opening  for  this  position  of  the  governor  should  be 
but  little,  if  any,  greater  than  that  specified  above. 

The  blocking  of  the  governor  should  now  be  changed,  fixing  it  in  such 
a  position  as  will  give  about  £  cut-off,  approximately  the  point  of  cut-off 
corresponding  to  the  rated  load.  This  point  of  cut-off  should  be  located 


124  VALVE   SETTING 

on  the  guides  by  making  marks  on  the  lower  guide  line  with  the  mark  on 
the  crosshead  shoe  for  each  dead-center  position,  and  dividing  the  distance 
between  them  into  three  equal  parts.  Now  turn  the  engine  over  until  the 
mark  on  the  crosshead  shoe  is  in  line  with  the  new  point  of  the  guide, 
corresponding  to  J  cut-off  for  the  head  end.  You  should  now  block  the 
governor  so  that  the  valve  is  line  and  line  at  the  steam  edge  by  taking  the 
measurements  from  the  templets  as  above  described. 

Next  turning  the  engine  over  until  the  valve  shows  the  cut-off  on  the 
crank  end,  when  it  will  be  noted  that  the  crosshead  has  not  traveled  tlu; 
full  £  stroke,  as  indicated  by  the  crosshead  and  guide  marks,  by  from  ^  to 
J  of  an  inch,  depending  upon  the  size  of  the  engine.  An  adjustment  of 
the  valve  endwise  will,  of  course,  lessen  this  amount,  but  will  increase  the 
differences  in  lead  between  the  two  ends,  so  that  this  adjustment  must  be 
made  to  the  best  advantage,  lead  and  cut-off  considered. 

To  determine  the  greatest  port  opening  for  any  point  of  cut-off,  the 
governor  can  be  blocked  for  the  desired  cut-off  and  the  engine  turned  over 
until  the  valve  begins  to  change  direction,  and  you  will  have  the  position 
of  maximum  port  opening  for  that  particular  cut-off. 

In  valve  setting  always  turn  the  engine  over  in  the  direction  it  runs, 
never  turning  it  past  a  point  you  desire  to  measure  and  then  turn  back  to 
it,  as  the  lost  motion  will  affect  accurate  adjustment. 

To  get  the  point  of  cut-off,  or  to  get  the  position  of  admission,  place 
the  templet  of  the  valve  on  the  templet  of  the  ports  to  a  position  where 
the  steam  edge  of  the  valve  is  in  line  with  the  steam  edge  of  the  port.  Take 
a  measurement  from  the  end  of  the  templet  corresponding  with  the  face 
of  the  cylinder  to  the  end  of  valve,  and  transfer  this  measurement  to  the 
valve  in  the  valve  chamber,  as  shown  in  Fig.  129.  Block  the  governor  in 
such  a  position  that  this  measurement  corresponds  to  that  just,  taken  from 
the  templet.  The  maximum  cut-off  is  usually  about  f  stroke. 

It  is  advisable,  but  not  absolutely  necessary,  to  determine  by  measure- 
ment all  events  of  the  stroke  including  lead,  port  opening,  cut-off,  release, 
and  compression,  and  make  a  note  of  each  measurement  for  both  ends  of 
the  stroke,  so  as  to  make  ready  comparison.  Release  will  be  earlier  on 
the  crank  end  than  on  the  head  end,  and  compression  will  be  earlier  on 
the  head  than  on  the  crank  end.  Both  of  these  events  by  measurement  will 
probably  be  uneven  by  from  £  to  1  in.,  depending  on  the  size  of  the  engine 
and  the  point  of  cut-off  considered.  The  nearer  to  the  end  of  the  stroke 
these  events  occur,  the  less  wjll  be  this  difference. 

If  great  care  is  taken  in  setting  the  valves  by  the  use  of  templets,  when 
an  indicator  is  placed  on  the  engine  and  cards  taken,  there  will  be  little 
adjusting  to  be  done.  There  is  no  reason  why  an  engine  cannot  be  set  in 
good  running  condition  by  the  above  method  without  the  assistance  of  an 
indicator  if  the  work  is  carefully  done. 


THE  FLEMING  PISTON-VALVE  ENGINES 


125 


COMPOUND  ENGINES 

In  taking  up  valve  setting  on  compound  engines,  the  first  point  to 
consider  is  what  work  the  engine  is  designed  for,  what  steam  pressure  it  is 
to  work  under,  and  whether  it  is  to  run  condensing  or  noncondensing. 

With  regard  to  tandem  compounds,  we  will  consider  the  two  types  of 
a  valve  gear;  first  the  one  in  which  the  valves  in  both  high-  and  low- 
pressure  cylinders  are  controlled  by  the  governor.  In  this  type  of  engine 
the  setting  of  the  valves  is  practically  the  same  as  for  the  simple  engine. 


FIG.  129. 

Of  course  both  valves  in  the  high-  and  low-pressure  cylinders  would  be 
set  independently,  giving  each  its  proper  amount  of  lead;  but  since  the 
governor  controls  both  high-  and  low-pressure  valves,  we  have  an  increased 
lead,  as  the  cut-off  becomes  later  for  both  valves.  The  load  for  the  high- 
pressure  valve  should  be  practically  the  same  as  for  the  simple  engine, 
while  that  of  the  low-pressure  cylinder  is  usually  from  three  to  four  times 
this  amount  in  order  to  get  theAmt-off  late  enough  and  give  ample  port 
opening. 

A  condensing  engine  has  usually  a  higher  cylinder  ratio  and  cuts  off 
earlier  in  the  low-pressure  cylinder  than  a  noncondensing  engine,  so  that 
the  low-pressure  valve  of  a  condensing  engine  should  have  less  lead  than 


126  VALVE  SETTING 

a  noncondensing  engine.  Compression  rises  less  rapidly  in  the  low-pres- 
sure cylinder  of  a  condensing  engine  than  in  a  noncondensing  engine,  so 
that  compression  should  start  earlier  in  the  stroke  of  a  condensing  engine; 
this,  of  course,  throws  the  release  later  in  the  low-pressure  cylinder  of  a 
condensing  engine  than  a  noncondensing  engine. 

It  would  be  difficult  to  state  here  how  much  lead  to  give  the  low- 
pressure  valve,  as  we  would  have  to  take  some  specific  engine  working 
under  some  fixed  conditions.  In  this  type  of  engine  the  load  will  remain 
practically  uniformly  divided  between  the  cylinders  throughout  the  full 
range  of  cut-off  from  minimum  to  maximum. 

The  above  construction,  where  the  governor  operates  both  valves,  is 
seldom  used  except  on  small  engines.  It  is  not  quite  as  flexible  for  adjust- 
ment as  where  the  low-pressure  valve  is  operated  by  an  independent 
eccentric. 

With  an  engine  of  this  type,  where  the  valve  on  the  high  pressure  is 
operated  by  the  governor,  and  the  valve  on  the  low  pressure  by  a  separate 


*  Port  ^N  port 

Face  of  Valve  Chamber 

FIG.  130. 

eccentric,  as  shown  by  Fig.  131,  proceed  to  set  the  high-pressure  valve 
in  the  same  manner  as  that  of  a  simple  engine.  Fig.  131  shows  the 
eccentric  used  on  the  low-pressure  valve  in  its  position  of  maximum  travel 
with  relation  to  the  crank  for  a  right-hand  engine  running  over.  This 
eccentric  is  so  constructed  that  its  center,  when  adjusted,  travels  across 
the  shaft,  thus  changing  the  cut-off  in  the  same  manner  as  in  the  high 
pressure. 

In  Fig.  131,  C  D  is  a  line  running  through  the  center  of  the  crank 
shaft.  A  B  is  a  line  running  through  the  eccentric  center  and  its  point 
of  suspension.  If  the  eccentric  is  so  arranged  that  the  center  line  of  the 
eccentric,  A  B,  is  brought  over  or  made  to  coincide  with  the  center  line 
C  D,  you  will  have  the  eccentric  at  its  minimum  point  of  cut-off. 

To  set  the  low-pressure  valve,  first  locate  the  eccentric  at  its  point  of 
minimum  cut-off,  or,  in  other  words,  have  the  points  G  H  F  and  the 
crank  (low-pressure  crank  if  it  be  a  cross  compound)  in  a  straight  line. 
Fasten  the  eccentric  with  the  set  screws  I  and  J,  then  turn  the  engine  over 
in  the  direction  in  which  it  runs  and  test  for  the  lead,  point  of  cut-off,  etc. 
For  the  best  adjustment,  have  the  point  of  suspension  F  slightly  behind 
the  crank,  so  that  when  the  eccentric  is  moved  by  the  screw  in  the  slot  from 
one  extreme  to  the  other,  the  lead  remains  nearly  constant.  Then  adjust  the 


THE  FLEMING  PISTON-VALVE  ENGINES 


127 


screw  E  for  the  point  of  cut-off  desired  by  giving  the  eccentric  a  greater 
throw  and  consequently  the  valve  more  travel. 

The  above  applies  to  the  cross-compound  engines  as  well  as  tandem 
engines,  with  the  exception  that,  when  setting  the  eccentric  on  the  low- 
pressure  cylinder  in  a  cross-compound,  the  eccentric  must  be  set  with  refer- 
ence to  the  crank  on  the  low-pressure  side. 

An  early  cut-off  in  the  low-pressure  cylinder  will  cause  a  high-receiver 
pressure  and  a  late  cut-off  a  correspondingly  low-receiver  pressure.  It  is 


c i—  B 


FIG.  131. 


advisable  to  so  adjust  the  cut-off  in  the  low-pressure  cylinder,  and  conse- 
quently the  receiver  pressure,  that  the  load  will  be  evenly  divided  between 
the  high-  and  low-pressure  cylinders  for  rated  load  conditions.  For  very 
light  loads  the  high-pressure  cylinder  will  then  carry  somewhat  more  than 
half  the  load,  and  for  overloads,  the  low-pressure  cylinder  will  do  slightly 
more  work  than  the  high-pressure  c}rlinder. 

This  is  not  at  all  objectionable,  either  from  the  viewpoint  of  economy 
or  otherwise,  as  repeated  tests  of  these  engines  have  shown.  The  varia- 
tion in  the  division  of  the  load  is  comparatively  slight. 

The  accompanying  table,  showing  the  effect  of  changing  steam  or  in- 
side lap,  exhaust  or  outside  lap,  travel  and  angular  advance,  for  piston- 
valve  engines  is  appended  for  convenient  references 


128 


VALVE  SETTING 


Admission 

Expansion 

Exhaust 

Compression 

Increase 
Inside  Lap 

Is  later 
Ceases  sooner 

Occurs  earlier 
Continues  longer 

Is  unchanged 

Engines  at 
same  point 

Increase 
Outside  Lap 

Unchanged 

Begins  as  before 
Continues  longer 

Occurs  later 
Ceases  earlie 

Begins  sooner 
Continues  longer 

Increase 
Travel 

Begins  sooner 
Continues  longer 

Begins  later 
Ceases  sooner 

Begins  later 
Ceases  later 

Begins  later 
Ends  sooner 

Increase 
Angular 
Advance 

Begins  earlier 
Period  unaltered 

Begins  sooner 
Period  the  same 

Begins  earlier 
Period  unchanged 

Begins  earlier 
Period  the  same 

FIG.  132.  —  VALVE  GEAR  OF  THE  PUTNAM  ENGINE. 


XIII 


THE    PUTNAM    ENGINE.* 

THE  high-pressure,  variable  cut-oft  engine  built  by  the  Putnam  Ma- 
chine Company,  of  Fitchburg,  Mass.,  and  known  as  the  Putnam  engine, 
presents  distinctive  valve-gear  features  which  should  interest  the  operating 
engineer.  There  are  four  "  double-beat "  poppet  valves,  all  operated  from 
a  single  lay  shaft  running  at  one  half  the  speed  of  the  main  shaft,  with 
a  range  of  cut-off  from  0  to  full  stroke.  A  general  idea  of  the  valve  gear 

may  be  obtained  by  examination  of 
Fig.  132,  which  shows  the  back  or 
valve-gear  side  of  a  left-hand  en- 
gine cylinder.  A  sectional  view  of 
the  valves  and  steam  passages  is 
shown  in  Fig.  135.  A  diagram  of 
the  side  shaft  is  shown  in  Fig.  134, 
valves  2  and  3  being  the  steam 
valves  and  1  and  4  the  exhaust, 
valves. 

To  set  the  valves  of  a  Putnam 
engine,  first  attach  the  regulator  to 
the  valve  gear,  raising  the  balls  of 
the  regulator  as  high  as  they  will 
go  and  holding  them  in  that  posi- 
tion (see  Fig.  133).  Then  push  in 
the  steam  levers  of  valves  2  and  3 
far  enough  to  allow  the  cams  which 
operate  them  to  be  turned  around 
on  the  shaft,  just  clearing  the  levers 
without  lifting  tlw  valve  as  shown 

x4  JLvjr.     !.>•>. 

in  Fig.  133.     While  the  levers  of  2 

and  3  are  in  position,  tighten  the  set  screws  in  the  rocker  arm  E,  Fig.  !:'»:'>, 
at  the  bottom  of  the  regulator,  when  the  balls  may  be  lowered  (Fig.  137) 
and  the  regulator  adjustment  is  complete. 

These  directions  regarding  the  regulator  refer  to  the  old-style  regu- 

*  Contributed  to  Power,  by  F.  L.  Johnson. 
130 


THE  PUTNAM  ENGINE 


132  VALVE   SETTING 

lator;  the  new-style  regulator,  Fig.  136,  is  somewhat  different  and  is 
operated  in  the  following  manner:  After  all  the  connections  have  been 
made,  raise  the  balls  until  the  clearance  8,  between  the  center  weight  and 
the  collar,  is  J  of  an  inch.  Hold  in  that  position  and  push  the  levers  of 
2  and  3  in  far  enough  to  allow  the  cams  to  operate  as  with  the  old-style 
regulator. 

If  the  engine  is  to  "  run  over,"  the  bevel  gear  at  the  end  of  the  lay 
shaft  should  occupy  the  position  of  E,  Fig.  133.    If  the  engine  is  to  "  run 


FIG.    135.  —  SECTIONAL   VIEW    OF   VALVES   AND   STEAM    PASSAGES. 


under,"  the  positions  of  the  collar  D,  Fig.  134,  and  the  gear  are  exchanged. 
The  lay  shaft  revolves  in  the  same  direction  in  all  cases.  The  changing 
of  the  position  of  the  gear  changes  the  direction  of  rotation  of  the  engine 
shaft.  The  question  of  direction  of  rotation  being  settled,  the  gears  are 
made  secure  in  their  respective  shafts,  and  the  crank  pin  put  on  the  center 
nearest  the  cylinder. 

Beginning  at  valve  2,  Fig.  134,  with  the  valve  closed,  make  a  mark  on 
the  valve  stem  -^  of  an  inch  below  the  packing  box,  turn  the  cam  by  hand 
in  the  direction  it  is  run  (Fig.  138)  until  the  mark  on  the  valve  stem  is 
flush  with  the  stuffing  box  and  make  the  cam  fast  to  the  shaft  by  means 
of  the  set  screw.  This  will  give  -jV-in.  valve  opening  when  the  crank  is 


THE   PUTNAM   ENGINE 


133 


on  the  center.  With  the  cam  of  exhaust  valve  4  proceed  in  exactly  the 
same  manner  as  with  steam  valve  2,  except  that  the  mark  on  the  stem 
should  be  T3¥  of  an  inch  below  the  packing  box.  Be  sure  that  the  set 
screws  in  both  2  and  4  are  set  up  securely  and  the  crank  is  opposite  center. 


FIG.    136.  —  NEW-STYLE    REGULATOR. 


FIG.    138. 


Proceed  with  steam  valve  3  exactly  as  with  2,  allowing  only  ^  of  an 
inch  lift  to  the  valve.  The  reason  for  doing  this  is  because  the  piston 
travels  much  more  slowly  in  the  crank  end  of  the  cylinder  than  in  the 


134  VALVE   SETTING 

head  end  and  does  not  need  the  same  amount  of  lead  to  secure  full  steam 
pressure  at  the  beginning  of  the  stroke.  Exhaust  valve  1  is  set  the  same 
as  4,  with  -j^-in.  rise. 

The  rock  shaft  which  operates  the  cam  levers  of  2  and  3  is  provided 
with  leather-lined  caps  to  the  bearings,  which  are  intended  to  furnish  the 
necessary  friction  to  prevent  unsteady  action  of  the  regulator.  These  caps 
should  be  tightened  just  enough  to  produce  the  desired  steadiness  and  no 
more,  for  if  undue  friction  is  induced  the  governor  will  be  prevented  from 
responding  quickly  to  a  change  of  load,  and  the  motion  of  the  engine  will 
be  unsteady. 

The  foregoing  instructions  are  intended  to  serve  for  setting  the  valves 
as  accurately  as  can  be  done  without  the  use  of  the  indicator.  After  the 
engine  is  in  operation  the  indicator  should  be  used  to  check  the  work  and 
secure  accuracy. 


XIV 
THE    STURTEVANT    COMPOUND    ENGINE* 

THE  setting  of  the  valves  and  the  adjustment  of  the  governor  and 
drainage  systems  of  any  make  of  engine  may  well  be  preceded  by  a  very 
brief  description  of  its  leading  characteristics.  As  shown  by  the  accom- 
panying sectional  view,  Fig.  139,  the  engine  in  question  is  of  the  vertical 
cross-compound  type,  with  the  cranks  at  180  degrees. 

The  high-pressure  cylinder  has  a  balanced  piston  valve  working  in  a 
removable  bushing  which  contains  the  ports;  it  takes  steam  on  the  inside 
and  exhausts  at  the  ends;  auxiliary  ports  in  the  valve  (see  Fig.  147) 
increase  the  port  opening,  during  the  admission  period,  preventing  wire- 
drawing. The  piston  valve  is  controlled  by  an  inertia  governor  which  is 
a  modification  of  the  Rites  type,  therefore  the  cut-off  in  the  high-pressure 
cylinder  is  automatically  changed  according  to  the  load. 

The  low-pressure  slide  valve  is  balanced  by  means  of  a  back  platen 
maintained  in  position  by  six  springs,  three  of  which  are  shown  at  A,  B, 
and  C,  Fig.  140.  These  springs  "fit  the  holes  D,  E,  and  F  in  the  valve- 
chest  cover.  The  low-pressure  valve  is  not  connected  to  the  governor,  and 
as  the  angular  advance  is  constant,  the  cut-off  in  this  cylinder  does  not 
vary  with  the  load,  but  is  fixed.  However,  the  low-pressure  eccentric  is 
adjustable;  that  is,  the  throw  may  be  changed  by  the  engineer  while  the 
engine  is  not  running.  The  adjustable  eccentric  permits  changing  the  lead 
and  cut-off,  for  altering  the  valve  travel  alters  these  events.  The  low- 
pressure  cut-off  occurs  at  practically  one-half  stroke  for  normal  load. 

It  is  well  to  set  the  low-pressure  valve  first,  for  this  operation  is  much 
easier  than  in  the  case  of  the  high-pressure  side.  It  is  first  necessary  to 
remove  the  tap  bolts  and  take  off  the  covers  leading  to  the  low-pressure 
valve  chest,  the  crank  case,  the  valve-rod  guide,  and  the  eccentric;  these  are 
shown  at  A,  B,  and  C,  Fig.  141,  and  at  D,  Fig.  144.  The  low-pressure 
crank  pin  should  be  put  on  the  top  center,  following  any  of  the  approved 
methods.  A  simple  operation  which  quickly  gives  the  position  with  suffi- 
cient accuracy  for  preliminary  valve  setting  is  to  turn  the  governor  wheel 
by  means  of  the  bar  until  the  face  A,  Fig.  142,  of  the  connecting  rod  is 
parallel  to  the  front  surfaces  B,  B  of  the  crank  arms. 

*  Contributed  to  Power,  by  Carl  S.  Dow. 
135 


FIG.    139.— SECTION    THROUGH   CYLINDERS   AND   VALVES. 


THE   STURTEVANT  COMPOUND   ENGINE 


137 


FIG.  140.  —  BACK  PLATEN  OF  LOW- 
PRESSURE  VALVE. 


The  throw  of  the  low-pressure  eccentric  should  now  be  adjusted,  the 
angular  advance  having  been  fixed  when  the  keyway  was  cut  in  the  eccentric 
hanger  which  is  shown  in  Fig.  143. 
But  before  this  can  be  done  the 
direction  of  rotation  must  be  de- 
termined. As  the  observer  is  now 
facing  the  low-pressure  end,  the 
engine  is  running  under  if  turning 
clockwise.  If  the  engine  is  to  run 
in  this  direction  (under),  move  the 
eccentric,  which  is  fulcrumed  to  its 
hanger  at  F,  and  fasten  the  pin  P 
at  the  extreme  left-hand  end  of  the 
slot  8.  This  gives  the  eccentric 
maximum  throw  and  the  valve  full 
travel.  Of  course  the  pin  P  should 

be  fastened  at  the  other  end  of  the  slot  if  the  engine  is  to  run  over.  When 
the  pin  P  is  in  the  center  of  the  slot,  as  shown  in  Fig.  143,  the  valve  has 
minimum  travel  and  no  lead,  because  the  lead  decreases  as  the  pin  ap- 
proaches the  center  of  the  slot,  for  this  operation  decreases  the  valve  travel. 
With  the  eccentric  fixed  for  full  throw  and  the  low-pressure  crank  pin 

on  the  top  center,  adjust  the  slide 
valve  for  a  lead  of  -/s  in.  at  the 
top,  that  is,  the  narrow  opening 
between  the  top  edge  Y  of  the  valve 
and  the  lower  edge  X  of  the  port 
should  be  -^  in.  See  Fig.  141. 
This  adjustment  is  made  by  alter- 
ing the  length  of  the  valve  rod  by 
means  of  the  nuts  at  N.  Both 
these  nuts  are  shown  at  the  right- 
hand  side  of  the  large  section  of 
the  engine,  Fig.  139.  The  low- 
pressure  crank  pin  should  now  be 
put  on  bottom  center.  The  lead  at 
the  bottom  should  be  ^  in.,  or,  as 
shown  in  Fig.  144,  the  distance 
(M  N)  between  the  edge  of  the 
port  and  that  of  the  valve  should 
be  J  in.  If  not,  equalize  the  error 
by  changing  the  leads,  making  one 
FIG.  i4i.-  LOW-PRESSURE  VALVE  SIDE  half  the  difference  at  the  top  and 
SHOWING  LEAD  ON  TOP  END.  one  half  at  the  bottom;  always  re- 


138 


VALVE   SETTING 


membering  that  the  bottom  should  have  a  little  more  lead  than  the  top. 

The  low-pressure  side  is  now  adjusted. 

Before  setting  the  high-pressure  valve  the  governor  must  be  considered. 

The  general  appearance  of  this  form  of  inertia  governor  is  shown  in  Figs. 

145  and  146,,  the  former  being  a 
view  of  the  side  next  the  engine. 
The  eccentric  is  not  keyed  to  the 
shaft,  but  is  free  to  move  across 
it  because  of  the  slot,  thus  chang- 
ing the  angular  advance  and  con- 
sequently the  cut-off.  The  eccen- 
tric and  weight  arm  of  the  governor 
are  both  rigidly  fastened  to  a  stud 
8,  which  passes  through  the  hub  of 
the  governor  wheel ;  the  eccentric  is 
thus  compelled  to  move  with  the 
weight  arm  and  its  position  varies 
as  the  stud  moves  nearer  or  farther 
away  from  the  shaft  center,  due  to 
inertia  and  centrifugal  force.  The 
disk  D,  Fig.  145,  is  the  oil  guard 
and  has  nothing  to  do  with  the 
action  of  the  eccentric.  When  the 

governor  wheel  is  stationary  the  tension  of  the  spring  is  such  as  to  allow 

the  weight  M  to  rest  against  the  stop  T,  Fig.  146,  in  which  position  the 

valve  has  maximum  travel  and  maximum  lead. 


FIG.    142.  —  AN   EASY   METHOD   OF  PUT- 
TING THE    ENGINE   ON  CENTER. 


To  SET  THE  HIGH-PRESSURE  VALVE 

To  set  the  high-pressure  valve  the  valve  plug  V,  Fig.  146,  and  the  cover 
at  D  must  be  removed.  With  the  piston  valve  enveloped  by  its  bushing, 
it  is  impossible  to  see  the  valve  itself,  except  at. the  top,  and  consequently 
the  lead  cannot  be  measured  directly  as  in  the  case  of  the  plain  slide  valve. 
The  setting  is  accomplished  by  measuring  the  distance  from  the  top  of 
the  valve  to  a  given  surface,  which  in  this  engine  is  the  top  of  the  valve 
chest  with  the  plug  or  cover  removed.  The  reference  edge  is  shown  at  T9 
Fig.  147. 

Since  the  piston  valve  takes  steam  on  the  inside,  the  inside  edges  of 
the  ports  in  the  bushing  are  the  important  ones.  Evidently  the  lead  is  tin1 
distance  the  inner  edge  of  the  valve  has  moved  from  the  inside  edge  of  tin- 
port  when  the  crank  is  on  the  center ;  therefore  when  the  valve  is  properly 
set  the  measurements  must  show  that  the  desired  lead  exists  in  the  valve 
chamber. 


«l 


FIG.    143.  —  ADJUSTABLE    LOW- 
PRESSURE    ECCENTRIC. 


FIG.    145.— THE   INERTIA 
GOVERNOR. 


FIG.    144.  —  LOW-PRESSURE    VALVE    SIDE 
SHOWING  LEAD   ON   BOTTOM    END. 


FIG.    146.  —  THE   GOVERNOR  IN 
POSITION. 


140 


VALVE   SETTING 


The  high-pressure  crank  should  be  placed  on  the  top  center.  The  lower 
edge  of  the  upper  port  is  5f£  ins.  below  the  top  surface  T  of  the  valve 
chamber.  Since  the  thickness  of  the  valve,  measured  from  its  top  surface 
to  the  steam  edge,  is  2T7g  ins.,  the  top  of  the  valve  should  be  3i  ins.  from 
the  reference  edge  T,  to  give  a  lead  of  \  in.  This  may  be  shown  as  follows : 


FIG.    147.  — THE   HIGH-PRESSURE    VALVE. 


— 2T\- — J  =  3J.  It  is  well  to  remember  in  this  connection  that  the 
valve  rises  to  open,  hence  the  lead  (J  in.)  is  subtracted  from  the  distance 
of  the  top  of  the  valve  to  the  edge  T  (see  Fig.  147). 

To  set  the  valve,  then,  it  is  only  necessary  to  put  the  high-pressure  crank 
on  the  top  center  and  adjust  the  length  of  the  valve  stem  to  make  the  top 
of  the  valve  3J  ins.  from  the  top  of  the  valve  chamber,  As  in  the  case  of 


THE  STURTEVANT  COMPOUND  ENGINE 


141 


the  low-pressure  valve,  the  stem  is  lengthened  or  shortened  by  means  of  the 
nuts  on  the  stem  at  the  slide. 

It  is  not  necessary  to  determine  the  lead  at  the  bottom,  because  the  valve 


FIG.  148. —THE  INDICATOR  RIG. 


and  its  bushing  are  designed  to  give  proper  lead  at  the  bottom  when  the 
top  lead  is  J  in.  The  same  method  of  measuring  is  followed,  the  only 
difference  being  due  to  the  location  of  the  lower  port. 


142  VALVE  SETTING 

After  replacing  the  covers  and  connecting  the  cylinder  drains  to  the 
sewer,  if  the  engine  is  to  run  noncondensing,  or  to  the  exhaust  pipe  if  con- 
densing, the  start  may  be  made.  The  reason  for  connecting  cylinder  drains 
to  the  exhaust  pipe  instead  of  to  the  sewer,  or  letting  the  drip  go  to  the 
atmosphere,  is  that  a  vacuum  cannot  be  maintained  if  the  cylinder  is  thus 
placed  in  communication  with  atmospheric  pressure. 

In  the  Sturtevant  compound  engine  there  are  two  drainage  systems :  one 
for  the  cylinders,  as  briefly  mentioned  above,  and  another  for  draining  wafer 
of  condensation  from  the  stuffing  boxes.  As  shown  in  Fig.  139,  small  pipes 
connect  with  the  depressions  at  the  valve  rod  and  watershed  partition  stuff- 
ing boxes.  The  condensation  collecting  at  these  points  is  led  through  the 
piping,  which  is  wholly  within  the  inclosing  frame,  and  delivered  to  the 
sewer.  The  rest  of  the  piping  within  the  frame  is  the  system  of  forced 
lubrication,  by  which  all  bearings  and  sliding  surfaces  are  supplied  auto- 
matically with  lubricant. 

To  start  the  engine,  if  condensing,  the  air  and  circulating  pumps  are 
first  put  into  operation  so  that  a  partial  vacuum  will  be  created  in  the  con- 
denser. Meanwhil^,  a  little  steam  should  be  allowed  to  warm  the  cylinders, 
the  condensation  leaving  by  the  cylinder  drainage  system. 

As  soon  as  convenient  the  indicator  should  be  attached,  for  the  valve 
setting  is  not  yet  final.  Fig.  148  shows  the  indicator  rig.  The  indi- 
cators are  located  at  the  three-way  cocks  A  and  B,  which  allow  steam  to 
enter  the  indicators  from  the  two  ends  of  the  cylinders.  The  reducing 
motion  consists  of  a  rod  R,  moving  vertically  in  a  projection  on  the 
door,  and  a  rocker  K,  which  transmits  the  crosshead  motion  to  the  rod 
R,  the  free  end  D  of  the  rocker  engaging  the  rod  R  at  C.  As  shown 
at  the  right-hand  side  of  Fig.  10,  the  rod  R  is  directly  below  the  indi- 
cator cord. 

When  a  moderate  speed  has  been  attained,  diagrams  should  be  taken 
simultaneously  from  the  cylinders  and  carefully  examined  for  defects  in 
valve  setting.  The  adjustments  to  be  made  depend,  of  course,  upon  the 
faults  revealed,  but  usually  slight  adjustments  in  the  lengths  of  the  valve 
stems  will  be  sufficient.  For  instance,  suppose  the  top  of  the  high-pressure 
cylinder  is  developing  more  power  than  the  bottom,  the  card  areas  may 
be  made  nearly  equal  by  shortening  the  high-pressure  valve  stem,  which 
will  bring  cut-off  earlier  at  the  top  and  later  at  the  bottom;  the  leads 
will  change  but  little,  that  at  the  top  decreasing,  and  that  at  the  bottom 
increasing.  The  same  principles  apply  to  the  low-pressure  side,  but  in 
general  the  low-pressure  valve  will  give  satisfactory  distribution  if  it 
was  carefully  set  during  erection  and  the  high-pressure  valve  is  properly 
adjusted. 


THE   STURTEVANT  COMPOUND   ENGINE  143 


ADJUSTING  THE  GOVERNOR 

The  only  remaining  adjustments  are  those  pertaining  to  the  governor. 
As  already  stated,  this  engine  is  regulated  by  a  modified  form  of  the  Kites 
inertia  governor,  which  has  been  so  universally  adopted  for  high-speed  en- 
gines that  a  description  is  unnecessary.  It  is  well,  however,  to  bear  in 
mind  a  few  of  its  fundamental  principles,  for  governor  adjustments  call 
for  a  knowledge  of  these  principles  rather  than  a  blind  following  of  direc- 
tions for  changing  certain  adjustments  because  of  certain  defects. 

The  governor  combines  both  the  centrifugal  and  inertia  effects :  the  for- 
mer controlling  the  speed  variations  caused  by  changes  of  load,  while  the 
latter  has  to  do  with  steadiness.  The  governor  arm  tends  to  maintain  its 
rotative  speed  due  to  the  inertia  of  the  heavy  weights.  If  the  load  increases, 
the  engine  tends  to  slow  down,  that  is,  the  rim  of  the  governor  wheel  will 
slow  down  but  the  weights  tend  to  move  at  the  same  speed  as  before.  The 
effect  of  these  two  movements  is  that  the  center  of  gravity  of  the  arm 
moves  inward,  increasing  the  load  and  lengthening  the  cut-off. 

If  while  the  load  changes  slightly  the  speed  is  steady,  but  lower  than 
desired,  the  tension  of  the  governor  spring  may  be  increased,  or  the  spring 
pin  P  moved  outward.  If  on  increase  of  load,  the  speed  drops  more  than 
it  should,  the  spring  pin  P  (Fig.  146)  may  be  set  nearer  the  governor  arm 
pivot  by  moving  it  along  the  slot,  or  the  weight  at  W  may  be  reduced,  and 
also  the  tension  in  the  spring.  In  short,  speed  regulation  consists  primarily 
in  balancing  the  spring  tension  against  the  centrifugal  force  of  the  arm. 
Exact  balance  at  all  points  in  its  movement  would  result  in  practically 
uniform  speed  from  no  load  to  full  load,  but  the  governor  would  then  lack 
stability,  hence  it  is  better  to  not  quite  balance  the  centrifugal  force,  so 
that  the  speed  will  drop  about  2  per  cent,  with  an  increase  from  no  load  to 
full  load. 

If  the  governor  is  unsteady,  and  requires  several  long  swings  of  the  arm 
to  correct  the  speed,  weight  may  be  added  to  the  long  end  of  the  arm  (M, 
Fig.  146),  or  the  spring  pin  P  may  be  moved  outward  in  its  slot. 

These  brief  remarks  regarding  the  governor  are  for  testing  plate  adjust- 
ments, but  it  is  assumed  that  the  valves  are  correctly  designed,  the  pins 
of  ample  size,  and  properly  lubricated.  After  long  service  wear  may  affect 
the  condition  of  the  parts  that  were  all  that  could  be  desired  when  on  the 
testing  plate.  When  in  poor  condition,  governor  adjustments  may  be 
slightly  different,  for  a  worn  valve,  scored  pin,  or  insufficient  lubrication 
may  be  the  fault  of  poor  speed  regulation. 

The  instructions  given  for  setting  the  valves  refer  to  the  Sturtevant  com- 
pound engine  having  cylinders  10  and  18  ins.  in  diameter,  and  a  stroke  of 
10  ins.  This  type  of  engine  is  built  in  other  sizes,  as  given  in  the  table 
on  page  144,  The  various  sizes  of  this  class  of  engine  vary  in  dimen- 


144 


VALVE   SETTING 


DETAILS  AND  MEASUREMENTS  OF  STURTEVANT  COMPOUND  ENGINES 


HlCH-PRESSURE  VALVE 

LOW-PRESSURE  VALVE 

1 

Laps 

Leads 

la 

n 

It 

2 

Laps 

Leads 

H 

|l 

P3(£ 

H 

SI/K  OF  ENGINE 

1 

ft 

g 

a 

1 

^m 

°o 

0 

a 

I 

a 

1 

5 

1 

H 
I 

1 

a 
C' 

I 

*o| 

1! 

|H 

6? 

E2 

"o 

pq 

H 

-3 

1 

ft 

,0 

| 

1 

| 

1 

£ 

*0> 

|| 

s 

1 

i 

C 

B 

x 

02 

^ 

O    ® 

&« 

02 

w 

1 

00 

^ 

§H 

H^ 
o 

1 

• 

CQ 

w 

X 

K 

61  -  10J-   X   6J 

2| 

H 

H 

0 

, 

A 

A 

If 

2H 

41 

2| 

u 

If 

0 

A 

A 

A 

*7    —  12     X   7 

24 

i 

z 

91 

8-14     X  8 

3* 

i 

I 

& 

j 

1% 

-i3ff 

2A 

2} 

5A 

31 

i* 

1A 

0 

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10    -  18     X10 

4| 

H 

i| 

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1 

1 

i 

2^ 

31 

6H 

41 

H 

H 

0 

H 

3^ 

i 

*  Valves  being  redesigned. 


sions  only,  therefore  the  valves  are  set  in  the  same  manner  for  all,  the 
measurements  differing  of  course.  The  above  table  gives  further  details 
and  important  measurements. 


XV 


THE  EICE  AND   SARGENT  ENGINE 

THIS  engine,  as  shown  by  the  cut  given  herewith,  is  of  the  heavy-duty 
Corliss  type,  primarily  designed  for  direct-connected  electrical  work  and 
for  operation  at  speeds  somewhat  higher  than  the  ordinary  Corliss  engine. 
The  motions  of  all  the  valve  parts  are  obtained  without  wrist  plates,  are 


FIG.  149. 

made  as  short  as  advisable,  and  all  parts  made  very  strong  with  unusually 
large  wearing  surfaces.  The  illustration  (Fig.  149)  represents  a  small, 
simple  engine.  The  company  also  builds  compound  engines  of  both  tan- 
dem and  cross  types  and  vertical  engines  of  large  sizes;  the  sizes  ranging 
from  150  horse  power  to  2,000  horse  power  on  single  cylinder  engines  and 
250  to  7,500  horse  power  or  larger  on  compound  engines.  Engines  of  1,000 
horse-power  rated  load  are  regularly  operated  at  150  revolutions  and 
smaller  engines. at  suitable  slightly  higher  speeds.  Engines  of  the  largest 
size  are  run  as  slow  as  75  revolutions. 

145 


146 


VALVE   SETTING 


Illustrations  are  shown  herewith  of  the  inlet  and  exhaust  valve  gears. 
The  operation  of  the  inlet  valve  gear  is  as  follows : 

Fig.  150  shows  the  inlet  valve  gear  for  the  front  end  of  the  cylinder 
in  its  extreme  left  and  opening  position.  The  latch  A  on  the  valvc-sinn 
lever  B  is  in  the  position  of  engagement  with  the  toe  C  on  the  rocker  D. 
The  pin  E  connects  through  the  intermediate  rockers  and  rods  with  the 
steam  eccentric  on  the  engine  shaft,  and  the  pin  F  connects  to  a  similar 
inlet  gear  at  the  back  end  of  the  cylinder.  As  the  rocker  D  moves  to  the 
right,  the  toe  C  engages  the  latch  A,  moving  the  inlet  valve  to  open,  and 
raising  the  dashpot  plunger  which  is  connected  to  the  pin  P.  Cut-off  is 
accomplished  by  the  toe  C  turning  downward  on  its  pivot  spindle  H  to 
release  the  latch  A.  The  spindle  H  has  a  cam  lever  I  rigidly  attached  in 


FIG.  150. 


FIG.  151. 


the  rear,  which  in  turn  is  carried  between  two  rolls,  J  J.  These  rolls 
turn  on  pins  in  the  cut-off  lever  K9  which  latter  turns  freely  on  the  valve- 
stem  journal.  The  arm  L  above  forming  part  of  the  same  casting  as  the 
cut-off  lever  K,  is  connected  to  the  governor  by  the  rod  M.  This  rod  is 
held  firmly  by  the  governor  and  does  not  move  unless  there  is  a  change 
in  the  speed  of  the  engine.  The  rod  N  connects  to  the  valve  gear  at 
the  head  end  of  the  cylinder.  The  latch  A  is  released  at  some  point 
in  the  opening  movement  of  the  rocker  D,  toward  the  right.  This  is  ac- 
complished when  the  rise  0  of  the  cam  lever  passes  between  the  cam 
rolls  J  J.  It  is  obvious  that  the  amount  of  valve  opening  and  the  length 
of  cut-off  depend  on  the  position  of  the  cut-off  lever  K,  as  controlled  by 
the  governor.  The  further  to  the  left  the  lever  K,  the  earlier  the  cut-off. 


THE  RICE  AND  SARGENT  ENGINE 


147 


Fig.  151  sjiows  the  rocker  D  at  the  extreme  right  of  its  motion.  Re- 
lease has  taken  place  and  the  valve  is  about  to  be  closed  by  the  pull  of  the 
dashpot.  The  valve  then  closes  promptly  and  the  lever  B  turns  to  the 
position  shown  in  Fig.  150.  The  cut-oft'  lever  K  is  here  shown  in  the 
position  giving  nearly  the  latest  cut-off,  which  is  about  three-quarter  stroke 
of  the  piston.  On  the  return  movement  of  the  rocker  D,  the  cam  rolls 
J  J  raise  the  cam  lever  I  and  the  toe  C  to  the  engaging  position.  At  the 
latter  part  of  the  movement  of  the  rocker  D  to  the  left,  as  the  toe  G 
passes  under  the  latch  A,  the  latter  is  raised  by  the  toe  sufficiently  to  clear 
the  same  and  the  latch  then  drops  by  gravity  in  front  of  the  toe  to  the 
engaging  position,  as  shown  in  Fig.  150. 

On  the  exhaust  gear  the  motion  of  the  eccentric  is  transmitted  through 
the  intermediate  rockers  and  rods  to  the  bell  crank  shown  in  the  illustra- 
tion Fig.  152.  The  motion  of  the  bell  crank  is  transmitted  to  the  exhaust 


FIG    152. 

lever  through  a  link,  thus  allowing  the  valve  to  pause  at  the  end  of  a  stroke. 
The  valves  of  the  engines  are  set  as  follows : 

Before  setting  the  valves,  see  that  the  lengths  of  all  valve-gear  rods  and 
clutch  rods  are  so  adjusted  that  all  the  valve  rockers  and  intermediate 
rockers  are  plumb.  These  are  the  rockers  shown  in  the  illustration  of  the 
complete  engine  herewith,  to  which  the  eccentric  rods  and  the  valve-gear 
rods  are  attached.  When  these  rockers  are  plumb,  rotate  the  eccentrics  on 
the  shaft  and  adjust  the  eccentric  rod  until  the  travel  of  the  intermediate 
rockers  on  each  side  of  the  plumb  line  is  equal.  Then  place  the  engine  on 
the  forward  center  and  make  coinciding  marks  on  the  crosshead  shoe  and 
the  slide.  Then  move  the  engine  backward,  so  that  these  lines  will  be 
^-in.  to  T5^-in.  apart.  This  will  give  from-j^-in.  to  -J-in.  valve  opening 
at  the  tfme  the  engine  passes  the  center.  Then  rotate  the  steam  eccentric 
on  the  shaft,  so  that  the  valve  and  port  will  be  line  and  line  and  moving 


148 


VALVE   SETTING 


to  open  the  valve.  The  arrangement  of  the  valves  in  the  cylinder  is  as 
shown  by  Fig.  153. 

To  set  the  exhaust  valves,  move  the  engine  back  about  3J  ins.  and 
set  the  eccentric  so  that  the  valve  and  ports  are  line  and  line  and  moving 
to  close  the  proper  valve.  Then  turn  the  engine  to  the  back  center  and 
repeat  this  operation,  only  turn  the  engine  back  more  than  3J  ins.,  and 
then  approach  the  marks  as  in  the  regular  operation  of  the  engine,  so 
as  to  get  out  all  back  lash. 

This  distance  of  3J  ins.  should  be  varied  through  quite  wide  limits 
to  give  more  or  less  compression  according  to  the  speed  of  revolution  of 


FIG.  153. 


the  engine  and  according  to  the  method  of  operation,  whether  condensing 
or  noncondensing. 

If  the  marks  do  not  come  exactly  the  same  as  at  the  front  end,  adjust 
the  eccentric  rod  to  make  up  one  half  of  the  difference  and  move  the 
eccentric  so  that  the  lines  on  the  valve  and  ports  again  come  together. 
The  whole  setting  should  now  be  repeated. 

At  all  times  have  the  length  of  the  rod  connecting  the  two  rocker 
levers  of  such  length  that  both  levers  will  be  plumb  at  the  same  time. 

On  the  low-pressure  side  the  steam  valve  should  be  set  to  open  about 
§  of  an  inch  from  the  end  of  the  stroke,  and  the  exhaust  valves  close  from 
6  to  8  ins.  from  the  end  of  the  stroke. 

On  tandem-compound  engines,  a  mark  should  be  made  on  the  front  end 
of  the  high-pressure  sole-plate  clamp  when  the  engine  is  cold;  then  when 
the  engine  is  thoroughly  heated,  measure  the  amount  the  high-pressure 
cylinder  has  moved  due  to  the  heat  expansion,  and  lengthen  out  the  long 


THE  RICE  AND  SARGENT  ENGINE 


149 


clutch  rods  the  same  amount.     The  valve  adjustment  will  then  be  prac- 
tically the  same  as  if  the  valves  were  set  with  the  engine  hot. 

The  steel  plates  on  the  latches  and  toes  should  lap  by  each  other  when 
engaged,  f$  in.  on  cylinders  up  to  22  ins.  diameter,  -f%  in.  on  cylinders 
from  24  ins.  to  and  including  30  ins.  and  ^  in.  on  cylinders  above  30  ins. 
diameter.  The  distance  the  latch  and  toe  plates  move  by  each  other  before 
engaging  is  adjusted  by  the  dashpot  rod,  and  should  be  kept  as  small  as 
practicable.  On  the  smaller  size  cylinders  this  amount  should  not  be 
less  than  -^  in.  and  should  not  exceed  -J  in.  on  the  largest  size. 


ADJUSTING  THE  RITES  INERTIA  GOVERNOR  USED  ON  RICE  AND  SARGENT 

ENGINES 

The  details  of  this  governor  are  as  shown  by  the  cut  given  herewith 
(Fig.  154).    This  illustration  shows  the  governor  in  the  shop  set  on  wooden 


FIG.  154. 

blocks  merely  for  the  purpose  of  photographing.  Its  position  on  the 
engine  is  shown  in  Fig.  149.  The  operation  of  the  governor  is  as  follows : 
The  governor  weights  are  caused  to  revolve  by  means  of  a  belt  acting 
on  the  pulley  shown  at  A.  The  circular  weights  shown  at  B  and  C  are 
suspended  on  pivots  shown  at  E.  These  weights,  due  to  the  centrifugal 
force,  tend  to  fly  from  the  center  and  are  held  from  flying  too  readily 
by  means  of  the  spring  D.  These  weights  are  connected  with  the  bell 
crank  E  by  means  of  the  arm  F  and  the  similar  arm  which  is  out  of  sight 
connecting  the  weight  C.  The  action  of  the  weights  on  the  rocker  E  is 
as  shown  by  the  sketch  given  above  the  cut,  the  points  G  and  H  repre- 


150  VALVE   SETTING 

senting  the  connection  of  the  arms  F  with  the  weights  B  and  C.  The 
points  G  and  H  are  compelled  to  move  in  a  straight  line,  since  the  revolv- 
ing weights  throw  directly  from  the  center.  Therefore  it  is  seen  that 
when  the  points  G  and  //  separate,  moving  toward  L  and  //,  the  point 
E',  which  represents  the  pivot  at  the  end  of  the  rocker  E,  is  compelled  to 
move  toward  the  point  M,  and  when  the  weights,  due  to  a  slackening  in 
speed,  approach  the  center  and  the  points  G  and  H  approach  the  point  K,  it 
is  seen  that  the  point  Er  would  move  toward  point  M'.  This  rocker  E  is 
rigidly  connected  to  the  shaft  8,  and  the  motion  of  the  weights  B  and  C 
imparts  an  oscillating  motion  to  the  shaft  8  which  is  transmitted  by  means 
of  the  mechanism  T  to  the  lever  N,  the  end  of  which  has  a  motion  in  an 
arc  of  a  circle  toward  N'  and  N".  The  governor  rod  connecting  with  the 
cam  collar,  which  determines  the  point  of  cut-off,  is  connected  at  this 
point  N.  A  retarding  dashpot  to  prevent  the  governor  being  too  sensitive 
is  connected  at  the  point  P. 

All  parts  of  the  governor  should  work  freely  and  all  cut-off  connections 
should  have  an  appreciable  endwise  movement  on  their  pins. 

The  governor  cross  shaft  must  be  perfectly  free  to  move.  The  governor 
may  be  made  more  sensitive  by  screwing  one  or  both  of  the  plugs  out  of 
the  spring,  and  less  sensitive  by  screwing  these  plugs  into  the  spring. 
One-half  turn  of  one  plug  is  sufficient  for  a  trial.  This  operation  neces- 
sitates removing  the  spring  from  the  governor  and  securing  it  in  a  vise. 

To  cause  the  engine  to  run  faster,  increase  the  tension  of  the  spring 
by  turning  the  spring  on  its  screws.  To  cause  the  engine  to  run  slower, 
reverse  this  operation.  One  turn  of  the  spring  will  usually  make  a  dif- 
ference in  speed  of  about  one  revolution  of  the  engine. 

ADJUSTING  THE  CUT-OFF  RODS  OF  THE  RICE  AND  SARGENT  ENGINE 

In  adjusting  the  cut-off  rods  on  the  high-pressure  side  of  a  compound 
engine,  or  on  a  simple  engine,  the  cam  slot  on  the  governor  is  so  designed 
that  with  the  governor  blocked  at  the  top  or  the  bottom  of  this  slot,  the 
position  of  the  cam  collar  on  the  valve  bonnet  will  be  the  same.  There- 
fore block  the  governor  at  either  the  top  or  the  bottom  of  this  slot  and 
adjust  the  rod  leading  to  the  forward  governor  rocker  so  that  the  latch 
and  toe  will  just  miss  connecting.  Then  adjust  the  governor  rod  be- 
tween the  front  bonnet  and  back  bonnet  so  that  the  back-end  latch  and 
toe  will  just  miss.  This  method  of  adjustment  will  give  the  greatest 
obtainable  range  of  cut-off  and  still  make  certain  that  no  steam  will  be 
admitted  to  the  high-pressure  cylinder  when  the  governor  is  clear  up  or 
clear  down. 

To  adjust  the  low-pressure  cut-off  rods,  first  equalize  the  cut-off  on 
the  front  and  back  ends  bv  means  of  the  cut-off  rod  between  the  front 


THE  RICE  AND   SARGENT  ENGINE  151 

and  back  bonnets.  Then  adjust  the  cut-off  rod  leading  from  the  gov- 
ernor cross  shaft  so  as  to  get  the  desired  receiver  pressure. 

On  condensing  compound  engines  a  receiver  pressure  of  10  to  15  Ibs. 
is  desirable,  with  an  initial  steam  pressure  of  100  to  150  Ibs.  On  non- 
condensing  compound  engines  with  the  same  initial  pressure,  the  receiver 
pressure  should  be  36  to  40  Ibs. 

The  low-pressure  cut-off  should  always  be  so  adjusted  as  to  allow  the 
low-pressure  steam  valves  to  open  slightly,  when  the  governor  allows  the 
toe  and  latch  to  pass  each  other  on  the  high-pressure  side.  This  adjust- 
ment is  made  after  the  proper  receiver  pressure  is  obtained,  and  will  pre- 
vent racing  on  light  loads  and  in  process  of  preparing  to  throw  the  load 
on  the  engine. 


XVI 


REYNOLDS    (1890)    AND   GIRDER  FRAME    CORLISS   EXGIXES 

THE  steam  valves  of  these  engines  admit  the  steam  under  the  valve 
edges  nearest  the  center  of  the  cylinder  and  while  the  valve  is  traveling 
away  from  the  center.  In  common  parlance,  they  admit  the  steam  "  un- 
der." The  steam  edge  of  the  cylinder  port  is  also  located  nearest  the  center. 
The  steam  edge  of  the  steam  port  and  that  of  the  valve  are  shown  in  Fig. 


FIG.    155, 


155,  at  A  and  A'.  Logically,  the  steam  exhausts  over  the  edges  of  the 
exhaust  valve  and  port  nearest  the  cylinder  center;  these  edges  are  shown 
at  B  and  B',  Fig.  155.  In  the  figures  the  direction  of  travel  of  both 
valves  when  opening  is  indicated  by  arrows. 

The  direction  of  travel  of  the  wrist  plate  when  the  crank-end  steam 
valve  is  opening  and  the  crank-end  exhaust  valve  is  closing  is  shown  by 
the  arrow  on  the  wrist  plate.  (At  the  same  time  the  head-end  steam  valve 
has  closed  and  the  exhaust  valve  is  open.) 

152 


REYNOLDS    (1890)   AND   GIRDER  FRAME   CORLISS   ENGINES      153 

The  working  edges  of  the  valves  and  ports  are  shown  by  radial  lines  on 
the  valve  end'  and  steam-chest  end,  when  the  back  bonnets  on  the  side  of 
the  cylinder  opposite  to  the  wrist-plate  side  are  off.  The  steam  and  ex- 


haust valves  both  indicate  lap  when  the  lines  on  the  valves  are  nearer  the 
center  of  the  cylinder  than  are  the  lines  on  the  chest.  This  condition  is 
shown  in  Fig.  157,  which  represents  the  end  of  one  steam  valve  and  chest 


O 


FIG.  157. 


with  the  back  bonnet  off.     The  line  A  on  the  valve  overlaps  the  line  B 
on  the  steam  chest  toward  the  center  of  the  cylinder. 


154 


VALVE   SETTING 


Fig.  155  shows  the  wrist-plate  central  for  adjusting  the  valve  connec- 
tions. There  are  three  marks  on  the  back  o"f  the  wrist-plate  hub  and  one 
mark  on  the  wrist-plate  stand,  which  is  bolted  to  the  cylinder,  the  marks 
appearing  as  in  Fig.  158.  When  the  lines  2  and  4  come  together  the  wrist 
plate  is  central;  when  1  and  4  are  opposite  each  other  the  wrist  plate  is 


FIG.  158. 

on  one  extreme  of  its  travel,  and  when  3  and  4  are  opposite  each  other  the 
wrist  plate  has  reached  its  other  extreme. 

To  set  the  valves  as  in  Fig.  155,  first  even  up  the  travel  of  the  rocker 
arm  and  wrist  plate,  according  to  the  instructions  for  setting  Corliss  valves, 
in  Chapter  V,  and  then,  placing  the  wrist  plate  in  its  central  position,  pro- 
ceed to  adjust  the  valve  rods  so  the  steam  and  exhaust  valves  will  have  the 
lap  given  opposite  the  cylinder  diameter  in  the  accompanying  table.  Set 
the  engine  on  the  center  and  move  the  eccentric  until  the  steam  valves  have 
the  lead  given  in  the  table. 


To  ADJUST  THE  LENGTH  OF  THE  DASHPOT  RODS 

* 
Referring  to  Fig.  159,  when  rod  //  is  down  as  far  it  will  go,  the 

shoulder  E  on  the  brass  hook  should  just  clear  the  steel  block  F  on  the 
valve  arm,  as  shown,  leaving  clearance  below  the  block,  as  at  G.     This 


REYNOLDS   (1890)   AND   GIRDER   FRAME  CORLISS   ENGINES      155 
TABLE  OF  LAPS  AND  LEAD  FOR  SETTING  VALVES 


Diameter  of  Cylinder 

Lap  of  Steam  Valves 

Lap  of  Exhaust  Valves 

Lead  of  Steam  Valves 

8 

A 

A 

A 

10 

A 

A 

A 

12 

A 

A 

A 

14 

\ 

1 

A 

16 

i 

I 

& 

18 

\ 

1 

31* 

20 

i 

i 

3Jj 

22 

A 

A 

A 

24       , 

A 

A 

A 

26 

A 

A 

A 

28 

A 

A 

A 

30 

A 

A 

A 

32 

1 

i 

A 

34 

i 

i 

T*ff 

36                                     | 

* 

A 

adjustment  of  the  rod  H  must  be  made  when  the  wrist  plate  is  at  its  ex- 
treme throw,  as  shown  by  a  mark  on  the  back  hub. 


156 


VALVE  SETTING 


HEAVY  DUTY  AND  "RELIANCE"  TYPES 

Figs.  160  and  161  are  views  of  the  cylinders  on  these  types  of  engine 
which  are  built  by  the  same  company.    In  design  these  engines  differ  from 


FIG.  160. 


those  illustrated  in  Figs.  155  and  156  in  having  less  heavy  wrist  plates  to 
suit  higher  engine  speeds,  and  in  being  equipped  with  double-ported  steam 
and  exhaust  valves. 


FIG.    161.  —  RIGHT-HAND  SIDE. 


REYNOLDS   (1890)   AND   GIRDER  FRAME  CORLISS  ENGINES     157 

Fig.  160  shows  the  wrist  plate  in  its  central  position,  with  the  valves 
lapped.  The  steam  is  admitted  over  and  through  the  valves,  the  steam 
edges  of  the  steam  valves  being  shown  at  A  and  the  working  edges  of  the 
two  ports — i.e.,  the  edges  away  from  the  center  of  the  cylinder  at  A'.  The 
exhaust  edges  of  the  exhaust  valves  and  ports  are  those  nearest  the  cylinder 
centers,  and  are  designated  respectively  B  and  B'.  The  arrows  show  the 
direction  of  travel  of  the  valves  when  opening. 

When  the  back  bonnets  of  these  valve  chests  are  removed,,  two  lines 
will  be  found  on  the  valves  and  two  on  the  chests,  marking  the  locations 
of  the  two  port  edges  on  each.  The  steam  valves  are  thereby  known  to  be 
lapped  when  the  lines  on  the  valves  are  farther  from  the  center  of  the 
cylinder  than  the  lines  on  the  chest,  and  the  exhaust  valves  lap  when  the 


FIG.    162.  —  LEFT-HAND   SIDE. 


lines  on  the  valves  are  nearer  the  center  of  the  cylinder  than  the  lines  on 
the  chest. 

To  set  these  valves,  proceed  as  in  Figs.  155  and  156,  with  the  exception 
of  providing  the  lap  for  the  steam  valves  in  the  manner  just  stated.  Allow 
the  amounts  of  lap  and  lead  given  in  the  table  already  referred  to,  which 
is  applicable  to  both  types  of  valve. 

Fig.  161  shows  the  position  of  the  wrist  plate  when  the  engine  is  on 
the  center  and  the  eccentric  is  advanced  to  give  the  steam  valves  proper 
lead.  The  adjustment  of  the  dashpot  rods  is  obtained  in  the  manner  de- 
scribed in  the  preceding  section  of  this  chapter. 

Fig.  162  shows  the  valve-gear  side  of  one  of  these  engines,  by  which  it 
will  be  seen  that  the  rocker-arm  motion  is  direct;  this  implies  that  the 
eccentric  should  be  advanced  ahead  of  the  crank  in  the  direction  of 
rotation. 


XVII 
THE   WEIGHT   STEAM   ENGINE 

WRIGHT  engines  were  designed  and  built  by  the  late  William  Wright 
and  many  of  them,  are  still  in  use  throughout  the  country.  During  the 
many  years  of  his  activity  in  the  engine  field,  Mr.  Wright  designed  a  num- 
ber of  different  types  of  valve  and  valve  motion  for  his  steam  engines.  In 
the  rotary-valve  engines  there  were  several  modifications  in  the  driving 
mechanism  and  of  the  flat  or  gridiron  valves  there  were  several  different 
shapes  of  valve  and  port,  but  in  the  latter  case  the  driving  mechanisms 
were  all  practically  the  same  in  detail  and  principle.  As  there  are  a  large 
number  of  Wright  engines  in  daily  operation,  an  explanation  of  the  setting 
of  the  gridiron  valve  should  prove  of  general  interest. 

Figs.  163  and  164  give  views  of  the  steam  and  exhaust  sides,  respec- 
tively, of  a  Wright  automatic  cut-off  engine  with  four  gridiron  valves  direct- 
driven  from  one  eccentric.  In  both  these  figures  the  eccentric  is  indicated 
by  A,  and  the  eccentric-rod  is  shown  at  B,  Fig.  164.  The  rock-shaft  D  D' 
extends  under  the  engine  frame  from  side  to  side,  and  on  each  end  of  the 
shaft  are  shown  the  rocker  arms.  In  Fig.  163,  E  represents  the  hook-rod; 
F,  the  steam  wrist  plate ;  G  G,  the  steam  valve  rods ;  H  H,  the  steam 
valve  cranks ;  /  7,  the  steam  valve  stems  and  yokes,  and  J  J  are  the  steam 
chest  covers.  The  same  parts  relating  to  the  exhaust  are  indicated  by  the 
same  letters  primed. 

VALVES  AND  VALVE  MOVEMENT 

Begulation  is  effected  by  a  pendulum  governor,  which  is  shown  in 
the  two  illustrations  just  referred  to.  When  the  governor  is  in  operation, 
the  balls  revolve  around  the  central  axis,  and  as  they  rise,  lift  the  vertical 
rod  a,  the  lower  end  of  which  is  shown  at  ~b,  Fig.  164,  where  it  is  attached 
to  the  arm  c  which  actuates  the  rock  shaft  d.  To  this  shaft  are  attached 
the  arms  e  e,  which  draw  the  splined  spindle  through  the  hollow  rock  shaft. 

Both  the  steam  and  exhaust  valves  work  vertically  and  are  actuated 
by  valve  stems  extending  downward  through  stuffing  boxes  in  the  bottoms 
of  the  chests.  The  steam  and  exhaust  wrist  plates  are  keyed  to  one  shaft, 
which  extends  under  the  cylinder  from  one  side  to  the  other,  so  that  they 
operate  at  the  same  time,  when  motion  is  imparted  by  the  hook  rod  E. 

159 


THE  WRIGHT  STEAM  ENGINE 


161 


The- two  shafts  which  carry  the  valve  cranks  are  hollow  and  stationary, 
each  Having  one  steam  and  one  exhaust  crank  on  their  respective  ends. 
The  main  steam  valve  stems  are  fastened  into  the  yokes  with  set  screws, 
and  on  their  lower  ends  the  yokes  are  provided  with  dash  pots,  which  also 
act  as  guides.  The  yokes  are  operated  by  steel  slides  which  are  fitted  into 
the  hollow  valve  crank  and  act  on  the  toes  held  in  the  yoke.  In  the  ex- 
haust valve  yokes  are  provided  sliding  blocks  to  which  the  valve  cranks 
are  secured  by  a  pin,  the  block  allowing  the  pin  center  to  change  its  posi- 
tion horizontally  as  it  moves  vertically. 

Of  the  four  gridiron  valves  with  which  the  Wright  engines  are  pro- 
vided, two  steam  and  two  exhaust  valves,  one  of  each  is  placed  on  one  side 
of  the  cylinder  and  a  similar  pair  on  the  opposite  side.  The  steam  valves 
are  V-shaped  and  partly  balanced, 
the  valve  seats  being  separate  and 
bolted  to  the  cylinders.  In  Fig.  165 
the  steam  valve  as  shown  at  a  a  and 
&  I  indicates  the  seat  over  which  the 
valve  rides,  permitting  the  steam  to 
pass  from  the  chest  through  the 
valve  and  seat  into  the  cylinder.  The 
exhaust  valves  are  shown  at  c  c,  Fig. 
165,  and  the  seat  at  d  with  a  plate  e  e 
to  hold  the  valve  against  the  seat. 

A  study  of  Fig.   166  will  give 
an  idea  of  the  arrangement  of  the 

valves  in  the  cylinder.  In  the  plan  one  end  of  the  cylinder  is  in  cross 
section,  showing  the  steam  and  exhaust  valves  for  that  end  in  their  relative 
positions.  The  elevation  shows  the  steam  valve  chest  with  the  valve  in 
position,  the  small  letters  having  the  same  significance  as  in  Fig.  165. 
In  Fig.  166  it  will  be  seen  that  A  is  the  steam  passage  to  the  valves  and 
B  the  exhaust  passage  away  from  the  cylinder,  but  to  understand  more 
fully  the  arrangement  of  the  mechanism  for  driving  the  valves,  reference 
should  be  made  to  Fig.  167,  in  which  A  is  the  elevation  of  the  steam 
wrist  plate  and  B  a  plan  view.  At  F  the  wrist  plate  is  in  its  central  posi- 
tion, with  the  cranks  H  II  and  the  yokes  I  I  in  the  same  relative  positions. 
On  one  end  the  yoke  is  shown  in  section  and  the  manner  in  which  the  steel 
slide  a  engages  the  steel  toe  &  in  the  yoke  is  also  indicated. 

When  the  wrist  plate  is  in  the  position  indicated  in  Fig.  167,  the  other 
valve-rod  pins  are  in  the  positions  shown,  and  when  the  wrist  pin  is  at  c 
at  one  extreme  of  its  throw,  the  other  valve-rod  pins  are  at  c1,  c2,  c*  and  c*, 
respectively.  By  the  time  the  wrist  pin  has  reached  its  other  extreme  of 
travel  at  d,  the  other  pins  are  at  d1,  d2,  d3  and  d*.  In  the  plan  B,  Fig.  167, 
is  shown  the  rock  shafts  e  e  with  the  steam  valve  crank  H  in  place  on  only 


b 

n 

o 

n 

(ZD 

n 

n 

CD 

c 

n 

FIG.  165. 


162 


VALVE   SETTING 


one  of  the  shafts.  The  splined  spindles  /  /  pass  through  the  hollow  -rock 
shafts  and  valve  cranks  as  shown,  and  on  one  end  is  a  nut  g  which  can 
be  adjusted  to  lengthen  or  shorten  the  spindles.  At  h  is  shown  the  key 
which  is  set  diagonally  across  the  end  of  the  spindle  and  engages  a  key- 
way  in  the  plate  a.  A  sectional  elevation  through  the  same  spindle  and 


shaft  is  shown  at  C,  and  at  i  is  a  bracket  which  helps  support  the  rock 
shaft  k. 

Fig.  168  illustrates  the  exhaust  wrist  plate  F',  which  is  on  the  same 
shaft,  only  at  the  end  opposite  to  that  occupied  by  the  steam  wrist  plate. 
It  will  be  noted  that  the  valve-rod  pins  in  the  wrist  plate  are  set  above 
the  center  of  the  plate,  while  those  in  the  steam  wrist  plate  are  on  the  same 


THE  WRIGHT   STEAM   ENGINE 


163 


line  when  set  central.    As  seen  in  Fig.  168,  the  valve  crank  Hf  is  fastened 
to  the  valve  yoke  T  by  a  pin  in  the  sliding  block  a. 


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FIG.  167. 


Both  the  steam  and  exhaust  valves  are  lapped  when  they  are  down  at 
the  lower  end  of  their  travel,  with  the  plunger  in  the  dash  pot  seated. 


164 


VALVE   SETTING 


When  traveling  up  the  valves  open,  and  close  in  coming  down,  but  to  get 
a  complete  understanding  of  the  movement  of  each  valve,  reference  should 
be  made  to  Figs.  169-172,  which  have  uniform  reference  letters.  The  valve 
is  shown  from  one  side,  but  this  must  not  be  mistaken  for  the  true  relative 
position  of  the  valve  to  the  valve  gear.  One  steam  valve  is  shown  only. 

In  Fig.  169  *  the  wrist  plate  F,  valve  crank  H ,  yoke  /  and  valve  a  are  in 
the  position  at  which  the  valve  is  lapped,  and  the  wrist  plate  and  eccentric 
are  on  the  center  of  their  travels.  The  center  line  A  A  is  horizontal 
through  the  wrist  plate  and  valve-crank  rockers,  B  B  representing  the  cen- 
ter of  the  wrist  plate  and  C  C  the  center  line  of  the  valve-crank  shaft.  The 


FIG.  169. 

dotted  line  D  D  shows  the  arc  in  which  the  end  of  the  plate  d  travels  when 
the  valve  admits  steam  during  the  full  stroke,  and  to  the  right  of  Fig.  169 
is  the  eccentric  circle  in  which  X,  X1,  X2  and  X3  are  separate  eccentric 
positions,  and  C  and  C"  are  two  separate  positions  for  the  crank.  The 
arrows  denote  the  directions  of  travel  of  each  part  at  this  central  position 
of  the  eccentric  and  wrist  plate. 

Bearing  in  mind  that  the  wrist  plate  on  the  opposite  side  is  operating 
the  exhaust  valve,  it  will  be  noted  that  when  the  steam  wrist  plate  and 
valve  crank  are  in  the  position  shown,  connected  by  the  rod  along  the 
line  G,  the  wrist-plate  pin  and  valve-crank  pins  for  the  exhaust  on  the 

*In  Figs.  169-172  the  plate  at  the  bottom  of  the  valve  yoke  I  is  not  shown  as  a 
swinging  plate,  on  account  of  the  small  scale  of  the  drawing.  It  is  correctly  given  on 
page  169. 


THE  WRIGHT   STEAM   ENGINE 


165 


opposite  end  are  at  c  c  connected  along  the  dotted  line  G'.  When  the  wrist 
plate  and  valve  crank  are  in  the  position  shown,  with  the  valve  lapped 
and  the  crank  at  its  center  C  on  the  eccentric  circle,  the  eccentric  will 
be  at  X.  Since  the  valve  opens  while  traveling  up,  all  the  parts  "must 
move  in  the  direction  denoted  by  the  arrows.  To  overcome  the  lap,  the 
eccentric  would  be  moved  up  to  X1,  and  then  to  give  lead  the  eccentric 
must  be  still  further  advanced  to  X~,  with  the  crank  still  at  C.  This 
gives  the  angle  at  which  the  eccentric  should  follow  the  crank,  and  if 
continued  together  in  their  travel  to  the  point  of  cut-off,  with  the  plate  d 
at  its  maximum  cut-off  position,  the  crank  and  eccentric  would  be  at 


Port  Opening 


FIG.  170. 

C2  and  Xs,  respectively,  or  the  crank  would  have  reached  90  per  cent, 
of  its  stroke. 

It  will  be  noted  that  the  movement  of  the  eccentric  is  enough  to  give 
a  travel  twice  the  width  of  the  port  and  lap  of  the  valve,  but  that  the 
valves  themselves  travel  only  far  enough  to  overcome  the  lap  and  port 
opening.  The  full  lines  show  the  valve  port  and  the  dotted  lines  the 
position  of  the  port  in  the  valve  seat.  The  dotted  lines  to  the  side  give 
the  relative  positions  of  the  valve  and  port  in  port  opening  and  lap,  and 
the  dotted  lines  to  the  side  of  the  valve  yoke  I  show  the  positions  to 
which  the  plate  d  must  lift  the  yoke  to  overcome  lap  and  give  full  open- 
ing. The  sum  of  the  two  is  the  valve  travel. 

Bearing  in  mind  that  the  eccentric  is  at  X,  with  the  wrist  plate,  valve 
crank  and  valve  in  the  positions  shown,  we  may  advance  one  step  in  the 
movement.  In  Fig.  170  the  position  of  the  wrist  plate,  valve  crank  and 


166 


VALVE  SETTING 


valve  are  shown  when  the  eccentric  is  advanced  to  the  point  X  on  the 
travel  to  give  lead  to  the  valve  with  the  crank  on  its  center  C.    The  crank 


FIG.  171. 


and  eccentric  will  now  travel   together.     The  relative  positions   of  the 
exhaust  pins  are  shown  at  c  c. 

Fig.  171  shows  the  valve  fully  opened,  having  reached  the  full  height 


FIG.  172. 


THE  WRIGHT   STEAM   ENGINE 


167 


of  its  travel.  The  eccentric  and  wrist  plate  are  also  at  the  extremes  of 
their  travels,  and  as  the  plate  d  is  so  far  extended  under  the  valve  yoke 
that  it  will  not  disengage,  the  valve  will  not  close  until  the  crank  and 
eccentric  have  so  far  advanced  in  their  travels  as  to  allow  the  valve  to  be 
lowered  far  enough  to  effect  cut-off,  which  is  shown  in  Fig.  172.  In  this 
figure  it  will  be  noted  that  the  direction  of  travel  in  the  wrist  plate,  valve 
crank  and  valve  have  been  changed,  and  cut-off  has  been  accomplished. 

As  shown  in  Fig.  167,  the  governor  acts  on  the  steam  valves  and 
effects  an  early  or  late  cut-off  through  the  medium  of  a  splined  rod  run- 
ning through  the  valve-crank  shafts ; 
when  the  rod  is  drawn  through  the 
hollow  valve  crank,  it  either  causes 
the  plate  not  to  pick  up  the  valve 
yoke  at  all,  or  allows  it  to  carry  full' 
stroke.  A  study  of  Figs.  174,  175, 
and  176  will  fully  explain  this 
action.  In  these  figures  A  A  is 
the  center  line  of  plate  d  and  valve 
yoke  I.  The  end  of  the  rod  is 
shown  at  8.  The  bottom  drawings 
are  plans  and  those  at  the  top  are 
elevation  views. 

In  Fig.  174  it  will  be  noted  that 
the  splined  end  of  the  rod  is  ex- 
tended tnrough  as  far  as  it  will  go, 
thus  making  the  plate  d  extend 
through  the  valve  yoke  to  its  posi- 
tion for  maximum  throw.  In  the 
elevation  the  line  D  D  shows  the 
arc  through  which  the  end  of  this 
plate  will  travel  while  operating  the 
valves.  When  the  conditions  are  as 
shown  in  Fig.  173,  the  governor 
should  be  at  rest  or  at  its  lowest 
point  of  operation.  The  rod  8  will 
then  be  ready  to  travel  in  the  direc-  FIG.  173. 

tion  of   the   arrow  when  the  gov- 
ernor takes  hold.    When  the  valve  gear  is  in  the  position  shown  in  Figs. 
169,  170,  171,  and  172  the  rod  8  and  plate  d  are  as  shown  in  Fig.  174. 

With  conditions  as  in  Fig.  174,  the  valve  is  given  its  full  maximum 
travel,  but  from  that  point,  as  the  governor  begins  to  pull  the  rod  ,8  in 
the  direction  of  the  arrows,  the  plate  d  travels  in  the  arc  of  circles  which 
grow  smaller  and  smaller  until  the  position  shown  in  Fig.  175  is  reached. 


168  VALVE   SETTING 

Here  it  is  shown  that  the  rod  8  has  been  drawn  out  to  half  the  distance 
of  the  length  of  the  splined  end,  and  as  a  consequence  the  plate  d  has 
been  drawn  back  until  the  arc  D  D  through  which  that  end  travels  has 
grown  smaller  and  does  not  lift  the  valve  so  far.  The  difference  in  the 
distance  to  which  the  plate  now  raises  the  valve,  and  the  distance  required 
for  full  port  opening  is  shown  at  /  and  g,  the  latter  reference  letter  in 
this  case  equaling  the  full  valve  travel.  The  eccentric,  always  moving  the 
same  amount,  throws  the  plate  d  along  the  line  D  D  enough  farther  to 
allow  it  to  disengage  itself  from  the  yoke  7,  and  the  latter  in  dropping 
causes  the  valve  to  cut  off.  This  event  occurs  when  the  piston  has  traveled 
about  one  fifth  of  its  stroke,  with  the  rod  and  plate  in  the  positions  shown 
in  Fig  175. 

When  the  governor  weights  have  reached  their  maximum  position  and 
the  engine  its  normal  speed,  the  splined  rod  is  drawn  out  still  farther 
until  the  plate  d,  Fig.  176,  will  not  engage  or  pick  up  the  valve  at  all. 
At  this 'point,  when  no  steam  is  admitted  to  the  cylinder  the  minimum 
valve  travel  has  been  reached. 

SETTING  THE  VALVES 

It  will  be  noted  that  the  valve  stems  set  down  in  the  valve  yokes  on 
a  shoulder  and  are  secured  in  place  by  a  set  screw.  This  does  not  allow 
of  easy  adjustment  of  the  length  of  the  valve  stem  or  valve  lap,  and  owing 
to  the  fact  that  the  valve  stems  are  not  easily  adjustable,  more  care  must 
be  taken  in  each  step  toward  setting  the  valves. 

First,  place  the  wrist  plate  in  its  central  position,  as  shown  in  Figs. 
167  or  169,  and  note  that  the  hook  pin  at  the  top  of  the  steam  wrist 
plate  is  not  on  the  vertical  center  line  of  the  plate,  but  is  off  center  a  few 
degrees  in  the  direction  of  the  cylinder  head  or  away  from  the  engine 
shaft.  The  two  steam  valve-rod  pins  on  the  wrist  plate  are  on  the  same 
center  line  as  the  wrist-plate  center,  and  when  these  pins  are  level  and  on 
an  exact  line  with  the  wrist  plate  and  valve-crank  centers,  the  wrist  plate 
is  on  the  center  of  its  travel.  It  is  a  good  plan  to  clamp  the  wrist  plate 
into  central  position,  while  doing  the  first  part  of  the  valve  setting,  by 
slacking  off  on  the  washer  on  the  end  of  the  stud,  placing  paper  under- 
neath and  clamping  down  on  that.  If  the  wrist  plate  is  keyed  on  the 
shaft,  it  can  be  held  in  place  with  a  thin  wedge  driven  between  the  boss 
of  the  wrist  plate  and  the  cap  of  the  bearing  next  to  it. 

Then  adjust  the  length  of  the  valve  rods  so  that  the  plate  d  in  the 
valve  crank  //  is  horizontal,  as  in  Fig.  169.  If  there  is  no  adjustment 
in  the  length  of  the  valve  rods,  then  note  whether  or  not  the  valve  crank* 
are  in  the  required  position  when  the  wrist  plate  is  central.  In  all  prob- 
ability they  will  be,  but,  if  not,  the  valve  rods  must  be  changed,  to  the 


THE   WRIGHT   STEAM  ENGINE 


169 


170  VALVE   SETTING 

proper  length,  even  if  they  have  to  be  taken  to  a  machine  shop  for  the 
purpose.  With  the  governor  in  its  lowest  position,  adjust  the  length  of 
the  rod  8  so  that  it  is  at  its  outer  extreme  position,  as  in  Fig.  174,  with 
the  plate  d  as  shown  here  and  in  Figs.  169,  170,  171  and  172.  Now 
hook  up  the  eccentric  rod  to  the  wrist  plate  and  free  the  latter  so  that  it 
will  work  and  roll  the  eccentric  slowly  around  the  shaft  in  the  direction 
it  is  to  run.  Carefully  note  the  length  of  travel  of  each  of  the  valves 
and  see  that  when  they  are  at  the  top  extreme  of  their  travel  that  the 
ports  are  open  no  more  than  in  Fig.  171.  If  both  the  valves  have  the 
same  travel  and  should  pass  over  the  edge  of  the  port  or  farther  than 
necessary  to  give  a  full  port  opening,  the  plate  d  may  be  extended  too 
far,  and  as  a  remedy  the  rod  S  should  be  shortened  so  that  the  valve 
can  be  raised  just  far  enough  to  give  the  full  port  opening.  If  the 
two  valves  travel  unevenly  they  must  be  adjusted  to  travel  alike,  and 
separate  adjustment  can,  of  course,  be  made  to  each.  If  the  valves  do 
not  travel  far  enough  to  give  a  full  port  opening  with  the  adjustment 
of  plate  d  as  in  Fig.  173,  then  something  must  be.  done  to  lengthen  the 
valve  stems. 

After  the  steam  valves  have  been  adjusted  the  next  thing  to  do  is  to 
set  the  exhaust  valves  so  that  they  will  travel  just  far  enough  to  give  a  full 
port  opening.  When  turning  the  eccentric  around  with  the  wrist  plate 
hooked  up,  a  mark  can  be  placed  on  the  wrist  plate  and  another  mark 
opposite  it,  at  each  extreme  of  the  travel,  on  the  hub,  adjacent  bearing 
cap  or  washer,  as  the  case  may  be.  With  dividers,  the  distance  between 
these  points  can  be  bisected  and  a  mark  made  to  center  the  wrist  plate. 
If,  when  the  mark  on  the  wrist  plate  is  brought  to  this  center  mark,  it 
does  not  appear  central,  as  in  Fig.  169,  then  the  length  of  the  eccentric 
rod  is  wrong  and  must  be  proven.  The  best  way  to  do  this  would  be  to 
make  a  new  set  of  marks,  first  placing  the  wrist  plate  central,  as  in  Fig. 
169.  Then  make  a  central  mark  on  both  wrist  plate  and  adjacent  cap  and 
lay  out  the  two  extreme  points  as  follows : 

In  Fig.  173  let  A  B  be  the  distance  from  the  center  of  the  wrist-plate 
hub  to  the  center  of  the  hook  pin,  A  C  the  distance  from  the  wrist-plate 
hub  center  to  the  surface  of  the  hub  or  washer  where  the  marks  are  to 
be,  D  E  the  travel  of  the  hook  pin  and  F  G  the  distance  apart  the  extreme 
positions  are  to  be. 

For  example,  let  A  B  =  10  ins.,  A  C  =  3  ins.,  D  E  =  5  ins.,  and 
F  G  =  ?  Then 

10:3::5:? 
(3X5)-r-10  =  1.5  ins. 

In  this  case  the  distance  between  the  extreme  points  would  be  1^  ins., 
and  taking  a  pair  of  dividers  and  setting  them  at  J  in.,  a  mark  could 


THE  WRIGHT  STEAM  ENGINE  171 

be  scribed  on  each  side  of  the  center  line  with  which  the  center  line  on 
the  hub  should  coincide  at  each  extreme  of  the  travel.  Turn  the  eccentric 
around  again  and  if  the  center  mark  on  the  hub  comes  short  of  one  mark 
and  over  the  other,  one  of  the  rods  is  too  long  or  too  short  between  the 
eccentric  and  the  wrist  plate. 

Note  whether  or  not  the  rocker  arm  travels  equally  on  each  side  of  the 
center  line,  which  should  be  exactly  vertical  when  the  eccentric  is  at  half 
stroke.  If  the  rocker  arm  does  not  travel  equally  on  each  side  of  the 
center  line,  as  for  illustration  from  D  to  B  and  B  to  E  in  Fig.  176,  the 
eccentric  rod  is  too  long  or  too  short  and  must  be  adjusted.  If  the  travel 
of  the  rocker  arm  is  correct  and  still  the  wrist  plate  does  not  travel  equally 
to  its  extreme  positions,  the  hook  rod  needs  adjustment. 

Having  equalized  the  travel  of  the  wrist  plate  and  valves,  proceed  to 
set  the  valves  for  running.  Place  the  engine  on  one  center  and  pull  the 
eccentric  around  until  there  is  lead  on  the  steam  valve  for  that  end,  and 
then  make  the  ccentric  fast  to  the  shaft.  Next  pull  the  engine  around 
and  observe  that  the  exhaust  valves  release  at  from  90  to  95  per  cent, 
of  the  stroke  and  that  the  steam  valves  cut  off  at  from  80  to  90  per  cent, 
of  the  stroke  for  the  maximum.  The  exhaust  valves  should  close  for 
compression  at  from  95  to  97  per  cent,  of  the  stroke.  Make  the  lead  of 
the  steam  valves  nearly  equal  with  a  trifle  more  on  the  crank  end. 

After  the  valves  are  set,  block  up  the  governor  to  its  highest  point, 
and  while  pulling  the  engine  around  one  complete  revolution,  see  that 
fhe  steam  valves  do  not  pick  up  at  all.  To  reverse  the  engine,  reverse  the 
eccentric.  If,  when  the  indicator  is  applied,  it  is  found  that  earlier  valve 
action  is  desired,  it  is  best  to  set  the  eccentric  ahead,  or  back  if  later 
action  is  desired.  To  get  an  earlier  steam  cut-off,  the  change  can  be  made 
on  the  rod  S,  Figs.  174,  175  and  176,  but  if  earlier  cut-off  is  secured 
in  this  way,  there  will  be  less  lead.  To  obtain  a  later  cut-off  in  this  way 
will  give  more  lead. 


XVIII 
THE    REYNOLDS    LONG-RANGE    CUT-OFF 

To  operating  engineers  in  general  the  Reynolds  long-range  cut-off  as 
manufactured  by  the  Allis-Chalmers  Co.  is  not  very  well  known.  On 
the  surface  there  appears  to  be  nothing  out  of  the  ordinary  in  the  valve 
gear  that  would  distinguish  a  Reynolds  from  any  other  Corliss  engine, 
but  upon  closer  inspection  some  essential  features  will  be  found  so  rad- 
ically different  that  they  will  cause  the  uninitiated  considerable  trouble 
until  the  movement  is  understood,  after  which  the  valve  gear  is  simplicity 
itself.  The  long-range  cut-off  is  designed  to  give  a  maximum  cut-off  for 
power,  and  the  essential  feature  of  the  steam  valves  is  that  they  have  a 
negative  lap  or  opening  when  in  mid  position,  the  cut-off  being  made 
entirely  by  the  governor  through  the  knock-off  cam. 

In  the  first  engine  of  this  design  built  by  Mr.  Reynolds  for  the 
World's  Fair  at  Chicago,  an  auxiliary  eccentric  operated  levers  on  the 
governor  in  such  a  manner  as  to  cause  the  knock-off  block  to  follow  the 
hook  until  cut-off  occurred,  but  in  all  details  the  valve  motion  is  appar- 
ently the  same  as  on  other  engines.  To  come  to  a  full  understanding  of 
the  peculiar  features  in  the  design  and  operation,  a  careful  study  of 
the  complete  movement  during  a  revolution  of  the  crank  is  necessary. 

Fig.  177  is  a  view  of  the  valve-gear  side  of  this  type  of  engine.  The 
eccentrics  are  in  the  case  A,  the  steam  eccentric  rod  is  indicated  by  B, 
and  the  exhaust  by  (7,  while  the  steam  and  exhaust  rods  are  respectively 
at  D  and  E.  It  will  be  noted  that  the  motions  from  the  eccentrics  to  the 
wrist  plates  are  direct.  The  steam  and  exhaust  wrist  plates,  valve  rods, 
etc.,  can  be  easily  traced  from  Fig.  177. 

To  obtain  the  first  impression  of  how  the  interior  of  the  valves  look, 
refer  to  Fig.  178,  in  which  the  steam  and  exhaust  valves  on  one  end  of 
the  cylinder  are  shown  with  the  valve  gear  removed  and  the  valves  and 
ports  in  cross  section,  while  on  the  other  end  the  valve  cranks  have  been 
left  in  place  and  show  their  relative  position  to  the  valves  at  the  opposite 
end.  The  steam  and  exhaust  wrist  plate*  are  shown  at  A  and  B,  respec- 
tively, and  above  A  is  shown  the  travel  circle  C  of  the  steam  eccentric; 
below  is  the  exhaust  circle  D.  In  these  circles  the  crank  position  is  at 
c,  and  e  is  the  eccentric  position.  The  steam-valve  crank  is  indicated  by 

172 


174 


VALVE   SETTING 


E,  the  exhaust- valve  crank  by  F ;  G  is  the  bell  crank  and  H  the  knock-off 
cam.  On  the  other  end  of  the  cylinder  where  the  valves  and  ports  are 
in  cross  section,  the  dotted  lines  E',  F' ,  G'  and  //'  denote  the  center  lines 
of  the  same  parts  on  that  end,  and  the  arcs  at  the  ends  of  these  lines 
show  the  respective  positions  of  the  pin  centers.  From  each  end  of  these 


FIG.  178. 


arcs  the  center  lines  show  the  positions  of  the  pins  when  they  reach  their 
respective  extremes  of  travel. 


STEAM    VALVES    OPEN    AT   BOTH    ENDS    WHEN    HOOKED   UP 

In  Fig.  178  the  wrist  plates  and  all  connected  parts  are  shown  in 
their  central  positions,  at  which  the  exhaust  valves  are  lapped,  as  is 
usual  in  practice,  but  the  steam  valves  are  open  on  both  ends  when  they 
are  hooked  up.  If  hooked  up  and  not  released  the  steam  valves  would 
be  open  from  the  beginning  of  one  stroke  up  to  75  per  cent,  of  the  return 
stroke,  but  when  the  knock-off  cam-pin  center  is  at  a,  the  cut-off  will 
be  carried  out  to  about  seven  eighths  or  eleven  twelfths  of  the  stroke,  and 
the  cut-off  will  occur  just  before  the  steam  valve  on  the  opposite  end  picks 
up  for  lead.  When  the  knock-off  cams  are  in  the  position  represented  by 
the  lines  H  and  H',  Fig.  178,  the  cut-off  will  occur  at  about  three  eighths 


THE  REYNOLDS   LONG-RANGE  CUT-OFF 


175 


of  the  stroke,  and  when  the  knock-off  pin  center  is  at  &  the  valves  will 
remain  lapped,  being  dropped  before  they  can  open.  If  the  regulator  is 
allowed  to  drop  down  so  the  knock-off  cam  pin  will  reach  the  point  c, 
the  valves  will  not  pick  up  and  will  remain  lapped.  This  peculiarity 
must  be  thoroughly  fixed  in  mind. 

When  an  ordinary  valve  is  at  the  center  of  its  travel,  it  is  lapped  on 
the  steam  edges  and  full  open  to  the  port  when  at  the  extreme  of  its 
travel  in  one  direction;  at  the  other  extreme  of  travel  it  is  closed.  With 
the  engine  under  discussion  the  steam  valves  are  lapped  at  the  extreme 


FIG.  179. 

throw  of  the  eccentric  in  one  direction,  and  full  open  at  the  other  extreme, 
having  minus  lap  when  at  the  center  of  travel. 

When  the  steam  valve  is  lapped  the  proper  amount,  the  dashpot 
plunger  is  down  at  the  bottom  of  its  travel,  and  the  cranks  E  and  Ef  are 
at  the  lowest  positions  of  their  travels.  The  eccentric  must  come  over 
to  its  extreme  position  in  order  that  the  valve  may  be  picked  up.  Owing 
to  the  dashpot  and  method  of  cut-off  on  a  Corliss  engine,  this  arrange- 
ment can  be  applied,  but  is  not  applicable  to  any  other  type  of  valve. 

For  the  purpose  of  illustration  let  it  be  assumed  that  the  steam  valves 
pick  up  and  do  not  cut  off  through  the  medium  of  the  knock-off  cam,  and 
let  us  follow  the  action  of  one  valve  through  one  revolution  of  the 


176 


VALVE  SETTING 


crank.  In  Fig.  179,  the  valve  cranks  are  in  their  extreme  positions,  and 
the  eccentrics  likewise,  with  everything  ready  to  start  in  the  direction  of 
the  arrows.  On  the  crank  end  the  steam  valve  is  lapped  and  the  exhaust 
valve  is  open,  while  reverse  2onditions  exist  on  the  head  end.  On  all  oilier 
types  of  valve  gear  the  eccentrics  would  be  advanced  90  degrees  when  the 
valves  are  lapped,  but  on  this  engine  the  steam  valve  is  lapped  when 
the  eccentric  is  on  its  extreme  position.  The  exhaust  valves  are  the 
same  as  on  any  other  double-eccentric  Corliss  engine. 

In  order   to   get   the   positions   of   the   eccentrics   in   relation    to   the 
crank,  we  will  advance  the  steam  eccentric  until  the  proper  amount  of 


FIG.  180. 

lead  is  obtained,  and  the  exhaust  eccentric  until  the  proper  amount  of 
closure  is  reached.  From  Fig.  180  it  will  be  seen  that  the  steam  eccentric 
is  only  some  30  degrees  in  advance  of  the  crank,  or  only  enough  to 
overcome  the  lap  and  lead,  and  the  exhaust  eccentric  follows  the  crank. 
Assuming  that  the  eccentrics  have  been  made  fast  to  the  shaft  in  these 
relative  positions,  we  will  now  move  the  crank  around  in  the  direction  of 
the  arrows  until  the  position  shown  in  Fig.  178  is  reached,  where  it  will 
be  noted  that  the  crank  has  advanced  on  the  first  half  of  its  revolution 
some  60  degrees  or  thereabout. 

In  Fig.  181  the  eccentrics  are  shown  in  their  extreme  positions  oppo- 
site to  that  at  which  they  started  and  the  steam  valve  is  shown  wide  open 


THE   REYNOLDS   LONG-RANGE  CUT-OFF 


177 


with  the  exhaust  valve  closed  as  far  as  it  will  go.  The  next  positions 
indicated  in  Fig.  182  show  the  steam  valve  closed  when  the  crank  has 
reached  approximately  75  per  cent,  of  its  return  stroke.  This  would,  of 
course,  prevent  the  practical  operation  of  the  engine  unless  the  regulator, 
through  the  knock-off  cam,  does  its  work  of  cutting  off  at  the  proper 
moment. 

It  is  well  to  bear  in  mind  that  when  the  steam  valve  carries  out  to 
the  latest  point  of  cut-off,  it  is  released  before  the  other  steam  valve  picks 
up  to  open,  and  that  while  the  release  of  the  steam  valve  varies,  the 
pick-up  does  not.  It  is  thus  impossible  for  both  steam  valves  to  be  open 


FIG.  181. 

at  the  same  time,  alth6ugh  they  may  appear  to  be  arranged  to  the  con- 
trary. On  an  ordinary  Corliss  engine  the  valves  will  hook  up  without 
releasing  when  the  regulator  is  at  its  lowest  working  position,  but  with 
this  type  the  valves  are  released  alternately  every  stroke,  no  matter  how 
low  the  regulator,  unless  it  is  in  the  safety  position,  when  the  valves 
would  not  pick  up  at  all. 

SETTING   THE    VALVES 

Bearing  these  points  in  mind  we  may  proceed  to  set  the  valves.     The 
amounts  of  lap  and  lead  and  the  positions  of  the  cranks  from  the  center 


178 


VALVE   SETTING 


lines  given  herewith  are  for  engine  cylinders  of  36-,  42-,  48-,  and  60- 
in.  stroke. 

First  set  the  wrist  plates  central  and  clamp  them  in  place;  then  adjust 
the  lengths  of  the  rods  so  that  the  steam  valves  are  open  i~|.  in., 
as  shown  in  Fig.  178,  and  the  exhaust  valves  are  lapped  -fa  in.  If 
the  rod  lengths  are  right  the  center  lines  of  the  cranks  E  and  E'  will 
coincide,  the  pins  of  the  cranks  F  and  F'  will  be  J  in.  from  the 
center  line,  as  shown,  and  the  pins  on  each  end  of  the  bell  cranks  0  and 
G'  will  be  2J  ins,  and  in.  from  the  center  lines.  When  the  valves 


FIG.  182. 

have  been  set  with  the  wrist  plates  central,  release  the  wrist  plates  and 
roll  the  eccentrics  around  the  shaft  to  test  them  and  the  reach  rods,  and 
see  that  they  are  of  the  right  length  to  make  the  wrist  plate  travel  equally 
each  side  of  the  center  line. 

Then  place  the  crank  on  center  and  pull  the  steam  eccentric  around 
enough  to  give  -^--in.  lead,  and  make  it  fast.  Next  move  the  engine 
around  in  its  direction  of  travel  to  about  95  degrees  of  its  stroke  and 
move  the  exhaust  eccentric  around  until  the  exhaust  valve  on  the  same 
end  is  just  opening  or  releasing.  Make  the  exhaust  eccentric  fast  and 
move  the  engine  around  its  full  revolution  and  check  off  the  valves  on 


THE   REYNOLDS   LONG-RANGE   CUT-OFF  179 

the  other  end  and  the  exhaust  closure.  Then  set  the  regulator  up  to  its 
central  position  and  adjust  the  lengths  of  the  rods  from  the  lever  to  the 
knock-off  cams,  so  that  the  pins  of  the  cams  H  and  H'  will  set  J  in.  off 
the  center  line,  as  in  Fig.  178.  Let  the  regulator  down  and  hook  up  the 
wrist  plates;  then  pull  the  engine  around  to  make  sure  that  the  steam 
valves  are  released  on  each  stroke  alternately  at  not  later  than  eleven 
twelfths  of  the  stroke,  and  always  before  the  other  valve  picks  up. 


XIX 
THE    DUPLEX    PUMP* 

As  is  well  known,  the  slide  valves  of  a  duplex  pump  have  neither  out- 
side nor  inside  lap.  This  is  necessary  to  prevent  the  pump  from  stopping 
should  the  valves  be  in  a  position  to  cover  all  ports.  By  making  the  length 
of  the  valve  the  exact  distance  from  the  outside  edge  to  the  outside  edge 
of  the  steam  port,  and  the  exhaust  cavity  the  exact  distance  from  the  inside 
edge  to  the  inside  edge  of  the  exhaust  port,  there  is  only  one  point  in  the 
travel  of  the  valve  where  ports  are  completely  closed;  and  it  is  not  likely, 
if  it  ever  should  happen  that  both  valves  were  in  this  position,  that  the 
pump  would  fail  to  start  off,  for  the  leakage  of  steam  past  the  edges  of 
the  valves  will  never  be  exactly  the  same  in  all  four  corners,  therefore  the 
equilibrium  would  be  destroyed  quickly. 

By  setting  the  outside  edges  of  the  valves  "line  on  line"  with  the  out- 
side edges  of  the  steam  ports,  the  valves  will  stand  in  a  central  position. 
If,  then,  both  rocker  arms  are  put  in  a  central  or  vertical  position,  the  clear- 
ance on  the  valve  rod  must  be  the  same  on  both  ends.  In  Fig.  183  this 
clearance  is  shown  inside  of  the  steam  chest  and  is  marked  C.  On  larger 
pumps  usually,  a  lost-motion  link  is  inserted  between  the  crank  and  the 
valve-rod  clevis,  which  can  be  adjusted  without  taking  off  the  steam-chest 
cover.  No  fixed  rule  can  be  given  for  the  amount  of  this  clearance,  as  it 
must  be  adjusted  to  suit  the  working  of  the  pump. 

On  a  pump  of  ordinary  proportion,  such  as  a  boiler  feed  pump,  the  total 
clearance,  2  (7,  should  equal  about  25  per  cent,  of  the  travel  T  of  the  crank 
pin  at  nominal  stroke.  On  a  low-service  pump  (also  on  a  pressure  pump 
for  moderate  pressure)  it  is  often  found  that  the  reciprocating  parts  are 
so  heavy  that  the  cushion,  with  the  cushion  valve  shut  tight,  is  not 
sufficient  to  stop  the  motion  of  the  piston  at  the  end  of  the  stroke.  In 
this  case  the  lost  motion  should  all  be  taken  up.  If  the  piston  does  not 
make  a  full  stroke,  the  lost  motion  may  be  increased  somewhat  above 
the  figure  given,  but  it  must  be  kept  in  mind  that  this  will  reduce  the 
travel  of  the  valve  and  the  port  opening,  and  thus  may  affect  the  speed 
of  the  pump.  , 

*  Contributed  to  Power  by  F.  F.  Nickel. 
180 


THE   DUPLEX  PUMP 


183 


THE  CROSS-EXHAUST  VALVE 


ist  closed.     The 
,re  cylinder^  and 

In  the  case  of  a  compound  pump  there  is  still  anothediate  space  and 
can  be  brought  into  action  to  regulate  the  length  of  the  tike. 

to  0.75  of  that 
3,  we  have  the 

low-pressu/ 


FIG.    183. 


is  a  connection,  provided  with  a  valve,  between  the  two  high-pressure  ex- 
haust pipes.    The  object  of  this  connection  is  to  equalize  the  pressure  in 


VALVE   SETTING 

pes  and  make  it  more  uniform.  This  is  called  the  cross 
influence  on  the  distribution  of  steam  is  clearly  shown  by 
inclusive.  Figs.  185  to  188,  inclusive,  are  convenient  sec- 


FIG.  184. 


tional  plans  of  the  steam  cylinders  of  a  compound  pump,  with  the  pistons 
in  positions  that  correspond  to  lines  A — B  and  B — (7  in  the  diagram  Fig. 


THE   DUPLEX  PUMP  183 

190.  Fig.  189  represents  a  diagram  with  the  cross  exhaust  closed.  The 
steam  pressure  follows  up  the  full  stroke  in  the  high-pressure  cylinder,  and 
when  the  exhaust  valve  opens  it  blows  into  the  intermediate  space  and 
mixes  with  the  steam  left  therein  from  the  preceding  stroke. 

Assuming  the  intermediate  space  to  have  a  volume  equal  to  0.75  of  that 
of  the  high-pressure  cylinder  and  a  cylinder  ratio  of  1  to  3,  we  have  the 
following  volumes : 

High-pressure  cylinder  =  1;  intermediate  space  =  0.75;  low-pressure 
cylinder  =  3. 

Clearances  are  neglected,  as  it  is  only  intended  to  show  the  action  of 
the  cross  exhaust.  We  will  also  assume  that  the  steam  expands  according 
to  Mariotf e's  law : 

p  X  v  =  constant, 

which  is  sufficiently  accurate  for  our  purpose,  and  assists  greatly  in  getting 
a  clear  conception  of  the  behavior  of  the  steam  as  it  passes  through  the 
various  stages. 

The  amount  of  steam  passing  through  one  side  of  the  engine  is  evidently 
one  high-pressure  cylinder  full  at  initial  pressure.  Its  measure  is  p  X  v  = 
120  X  1  =  120  Ibs.  When  the  high-pressure  exhaust  valve  opens,  this 
steam  flows  into  the  intermediate  space,  where  it  meets  and  mixes  with 
steam  that  was  left  there  from  the  preceding  stroke.  This  steam  was  shut 
off  from  its  communication  with  the  steam  in  the  low-pressure  cylinder 
when  its  exhaust  valve  opened  and  must  be  at  the  same  pressure  as  the  steam 
in  the  low-pressure  cylinder  at  the  point  of  exhaust.  As  the  ratio  of  cyl- 
inders was  assumed  to  be  as  1  to  3,  the  steam  expands  three  times  as  it 
passes  from  the  high-pressure  cylinder  to  the  low-pressure  cylinder,  and  the 
terminal  pressure  is  therefore 

120 

=  40  Ibs. 

3 

It  will  be  noted  that  120  is  a  measure  for  the  steam  passing  through  the 
engine  and  this  amount  is  accounted  for  by  the  indicator  diagram  at  every 
point  of  the  stroke.  Thus  we  have : 

High-pressure  cylinder,  p  X  v  =  120  X  1  =  120. 

Low-pressure  cylinder,  pX^  =  40X3  —  120. 

The  amount  of  steam'  that  is  constant  and  remains  in  the  intermediate 
space  is  0.75  X  40  —  30  Ibs. ;  the  two  combined  give  120  +  30  =  150  Ibs., 
which  when  distributed  over  a  volume  of  1  +  0.75  ==  1.75  results  in  a  pres- 
sure of 

150 

=  85  Ibs. 

1.75 


184 


VALVE   SETTING 


This  means  that  when  the  high-pressure  exhaust  valve  opens  the  steam 
expands  from  the  high-pressure  cylinder  into  the  intermediate  space  from 
120  to  85  Ibs.  without  doing  any  useful  work.  From  85  Ibs.  it  then  ex- 


Left  Hand  Side 


Right  Hand  Side 


FIG.    185. 


Left  Hand  Side 


Right  Hand  Side 


FIG.    186. 


pands  from  the  high-pressure  cylinder  through  the  intermediate  space  into 
the  low-pressure  cylinder  doing  useful  work  upon  the  1<>\\ -pressure  piston. 

With  two  points  of  the  expansion  curve,  namely,  85  ll>s.  at  the  begin- 
ning and  40  Ibs.  at  the  end  of  the  stroke,  it  is  now  easy  to  construct  the 
remainder  of  the  curve,  as  it  is  only  necessary  to  complete  the  rectangle 


THE   DUPLEX  PUMP 


185 


and  draw  the  diagonal.  Where  this  diagonal  meets  the  line  of  zero  pres- 
sure, there  is  point  o,  the  zero  point  of  pressure  and  volume.  Any  line 
drawn  through  this  point  o  will  give  the  volume  on  the  line  85,  Fig.  189, 
and  its  corresponding  pressure  on  line  A,  Fig.  190. 


.7ft  Volume 


40  Lb. 


FIG.    187. 


FIG.    188. 


Under  the  conditions  indicated  in  Fig.  189,  it  cannot  he  expected  that 
an  ordinary  pump  will  work  satisfactorily,  as  the  following  comparison  of 
the  steam  forces  will  show: 


186  VALVE   SETTING 

Beginning  of  stroke: 

H.  P.,  120  -  85  =  35 

L.  P.,  85  -  6  =  79  X  3  =  237 

Total  steam  force.  .          .  272  Ibs. 


End  of  stroke: 


H.  P.,  120  -  40  =  80 

L.  P.,  40  -  6  =  34  X  3  =  102 

Total  steam  force  .          .  182  Ibs. 


The  average  of  the  two,  or 

272  +  182 


=  227  Ibs., 


is  a  measure  of  the  resistance  which,  in  a  pump,  is  constant  throughout  the 
stroke.     There  is,  therefore,  at  the  beginning  of  the  stroke,  a  surplus  of 


61— 


FIG.    189. —CROSS   EXHAUST  CLOSED. 

272  —  227  =  45  Ibs.,  and  at  the  end  a  deficiency  of  227  —  182  =  45  Ibs. 
If,  however,  the  cross  exhaust  is  opened,  it  equalizes  these  two  forces  to  a 
certain  extent  and  modifies  the  diagram,  as  shown  in  Fig.  190. 

With  the  assistance  of  Figs.  185  to  188,  inclusive,  it  is  easy  to  follow 
the  steam  through  its  various  stages.  In  Fig.  185  the  pistons  of  the  right- 
hand  side  have  completed  the  stroke  and  are  about  to  return.  The  cylinders 
on  the  other  side  and  intermediate  spaces  are  filled  with  steam  at  the  low- 
pressure  terminal,  or  40  Ibs.  The  total  amount  of  steam  is  then 


120  X     1  = 

40    X  3.9  = 

Total  . 


120 
156 

276 


THE   DUPLEX  PUMP  187 

which  divided  by  the  volume,  4.9,  gives  a  resulting  pressure  of 

276 

=  56.5  Ibs., 

4.9 

as  shown  in  Fig.  186.  This  increased  pressure  gives  the  low-pressure  piston 
of  the  left-hand  side  an  additional  push  and  enables  it  to  complete  its 
stroke  while  the  steam  expands  down  to  40  Ibs.  again.  Then  the  steam 


40 


H.P. 


L.P. 


56.5 


FIG.    190. —  CROSS   EXHAUST   OPEN. 

from  the  left-hand  high-pressure  cylinder  flows  into  the  intermediate  space 
and  raises  the  pressure  to  56.5  Ibs.  in  order  to  help  out  the  right-hand  low- 
pressure  piston. 

Fig.  190  shows  this  action  clearly,  but  in  practice  the  rise  in  pressure 
will  not  be  as  abrupt  as  shown  there,  as  the  pulsations  in  the  pipes  will  still 
more  equalize  the  differences  and  produce  a  practically  uniform  pressure 
in  the  intermediate  space. 

It  will  also  be  noted  that  by  opening  the  cross  exhaust,  pressure  is  re- 
moved from  the  low-pressure  piston  and  shifted  over  to  the  high-pressure 
piston,  which  results  in  a  loss  of  power  and  reduced  speed  of  the  pump. 

The  cross  exhaust  should  therefore  be  kept  closed  whenever  the  pump 
runs  fairly  well  in  this  condition. 


XX 

AIK    COMPRESSORS* 

IJST  an  air  compressor,  as  well  as  in  a  steam  engine,  clearance  between 
the  piston  and  cylinder  heads  has  to  be  allowed,  for  mechanical  reasons, 
when  the  piston  reaches  the  end  of  its  stroke.  This  clearance  space  is 
augmented  by  the  cubical  contents  of  the  suction  and  discharge  ports,  the 
pockets  for  piston-rod  nuts,  etc.  The  clearance  volume  should  be  made 
as  small  as  possible  for  the  following  reasons : 

(a)  To  diminish  the  friction  loss  due  to  compressing  and  reexpanding 
of  the  air  confined  in  the  clearance  space  at  the  end  of  the  stroke. 

(&)   To  attain  as  high  volumetric  efficiency  as  possible. 

(c)  To  avoid  the  slow  opening  of  suction  valves,  which  increases  the 
suction  loss. 

Using  the  same  lettering  to  distinguish  the  various  sections,  an  ex- 
planation of  these  points  may  be  made  as  follows: 

(a')  The  energy  contained  in  the  air  confined  in  the  clearance  space 
ought  not  to  be  lost;  this  air  should  be  reexpanded  on  the  return  move- 
ment of  the  piston,  thus  giving  back  most  of  the  work  required  for  its 
compression.  Part  of  this  work,  however,  will  be  lost  in  the  friction  of 
the  air  compressor  and,  on  account  of  the  work  unavoidably  expended  in 
friction  during  the  compression  and  reexpansion  of  the  air,  it  is  desirable 
to  make  the  clearance  volume  as  small  as  possible. 

(&')  The  suction  air  valve  must  not  be  opened  before  the  compressed 
air  in  the  clearance  space  has  been  reexpanded ;  if  it  is  opened  before  the 
pressure  has  been  reduced  by  such  expansion  to  that  of  the  air  supply,  com- 
pressed air  will  rush  out  through  the  suction  ports  and  the  energy  stored 
up  in  this  air  be  lost.  The  larger  the  clearance  the  later  the  suction  valve 
should  be  opened  for  the  admission  of  fresh  air;  consequently,  the  smaller 
will  be  the  quantity  of  fresh  air  taken  in,  and*  the  capacity  of  the  com- 
pressor is  correspondingly  reduced.  The  volumetric  efficiency  of  a  compres- 
sor is  the  ratio  of  the  volume  of  air  in  cubic  feet  taken  in  through  the 
suction  valves  to  the  displacement  of  the  piston  in  cubic  feet,  provided 
the  valves  are  tight. 

To  show  the  influence  of  an  increase  in  clearance  on  the  volumetric 

*  Contributed  to  Power  by  Claude  Aikeus. 
188. 


AIR  COMPRESSORS  189 

efficiency  of  an  air  compressor,  let  us  assume  a  22  X  36-in.  air  compressor 
taking  air  in  at  atmospheric  pressure,  discharging  it  at  30  Ibs.  gauge  and 
having  1J  per  cent,  clearance,  as  compared  with  one  having  5  per  cent, 
clearance. 

The  cylinder  volume  being  proportional  to  the  stroke,  the  clearance 
volume  may  be  expressed  in  inches  of  stroke;  thus,  1^  per  cent,  clearance 
equals  0.015  X  36  ^=  0.54  in.  of  stroke.  The  air  confined  in  the  clearance 
space  expands  very  nearly  adiabatically ;  that  is,  not  losing  any  heat  to 
its  surrounding  walls  or  receiving  any  from  them,  especially  if  the  heads 
of  the  air  cylinder  are  not  cooled.  The  formula  for  adiabatic  expansion 
of  air  is: 

P  V  1.41  =  Constant, 
where 

P  —  pressure  per  square  inch, 
and 

V  =  volume  in  cubic  feet. 

The  part  of  the  stroke  required  for  the  reexpansion  of  air  from  44.7 
to  14.7  Ibs.  absolute  is 

:4.7\  1  1 

(  0.54  =  0.648. 


K44.7\      1 
nyJiTi- 


The  volumetric  efficiency,  as  far  as  clearance  is  concerned,  is  therefore 
36-0.648 


36 


=  0.982; 


or  the  capacity  of  the  air  compressor  is  100  —  98.2  =  1.8  per  cent,  less 
than  the  piston  displacement. 

As  the  percentage  of  decrease  in  capacity  is  directly  proportional  to  the 
percentage  of  clearance,  with  5  per  cent,  clearance  the  capacity  will  be 
decreased 

5X1.8 

— — —  =  6  per  cent. 
1.5 

(c')  Another  and  very  important  reason  for  desiring  small  clearances 
in  air  compressors  having  positively  operated  suction  valves  is  that  the 
opening  of  the  suction  valve  becomes  the  slower  in  relation  to  the  speed 
of  the  piston  the  later  it  opens,  or,  in  other  words,  the  larger  the  clearance. 

If  the  suction  valve  begins  to  open  when  the  piston  moves  at  a  com- 
paratively high  speed,  the  air  has  to  assume  a  high  velocity  in  order  to 
follow  the  piston.  As  a  consequence,  the  pressure  in  the  air  cylinder 
will  be  considerably  lower  than  that  of  the  outside  air  and  the  work  the 
compressor  has  to  do  is  uselessly  increased. 


190  VALVE   SETTING 


DETERMINING  RELATIVE  POSITIONS  OF  CRANK  PIN  AND  ECCENTRIC 

The  relative  positions  of  the  crank  pin  and  eccentric  may  be  determined 
graphically  or  by  calculation. 

Assuming  the  same  conditions  as  stated,  the  part  of  the  stroke  required 
for  reexpansion  from  44.7  Ibs.  absolute  to  14.7  Ibs.  absolute  is  0.648  in. 
Graphically,  proceed  as  follows:  In  Figs.  191  and  192  draw  the  crank-pin 
circle,  R  =  18  ins.,  and  find  the  ends  of  stroke  of  compressor,  2R  =  36  ins., 
by  laying  off  the  length  of  the  connecting  rod,  L  =  108  ins.,  from  the 
extreme  crank-pin  positions;  then  measure  the  points  X  —  0.648  in.  from 
each  end  of  the  stroke,  giving  the  piston  positions  at  which  the  suction 
valve  should  open.  With  L  as  a  radius  and  the  points  X  from  the  ends 
of  the  stroke  as  centers,  determine  the  points  of  intersection  with  the 
crank-pin  circle.  This  gives  the  positions  of  the  crank  pin  at  which  the 
inlet  valve  should  open. 

By  calculation  the  crank  angle  corresponding  to  a  piston  movement  of 
0.648  in.  is: 

For  head  end  (see  Fig.  191), 

7">2       I       T?2  T  2  "V    /  c\  T  T7"  V 

^  K~  -j-  B*  —  L2    i  X  (2L  —  X) 

•/  ODD  nv/T  ~v     i      r>\ 


0.648  (216  -  0.648) 

=  0.96908 


=  1-36  (108  -  0.648  +  18) 

=  14  degrees  17  minutes. 

For  crank  end  (see  Fig.  192), 

L2  -  R-  -  B-  X(2L 


2KB  2R(L-R 

0.648  (216  +  0.648) 
=  1~  36  (!08  -  !8  +  0.648)  = 
=  16  degrees  52  minutes. 

The  suction  valve  on  the  crank  end  should,  therefore,  open  when  the 
crank  has  moved  16  degrees  52  minutes  past  the  dead  center  and,  of  course, 
it  should  close  just  when  the  crank  reaches  the  .inner  dead  center,  so  that 
the  suction  valve  opens  and  closes  while  the  crank  travels  through  an 
angle  of 

180  degrees  —  16  degrees  52  minutes. 

The  eccentric  moves  through  the  same  angle  as  the  crank,  and  its 
opening  motion  must  be  equal  to  its  closing  motion;  it  has,  therefore,  an 
equal  amount  of  motion  on  each  side  of  the  horizontal  center  line  during 


AIR  COMPRESSORS  191 

the  suction  period  of  the  compressor.  The  position  of  the  eccentric,  when 
opening  the  suction  "valve,  must  be 

180  degrees  —  16  degrees  52  minutes 

—  81  degrees  34  minutes 

from  the  inner  dead  center,  the  valve  gear  being  designed  with  the  eccentric 
leading  the  crank. 

Due  to  the  angularity  of  the  connecting  rod,  the  position  of  the  eccen- 
tric for  the  forward  and  return  stroke  would  not  be  the  same.  A  com- 
promise may  be  made,  but  it  is  sufficient  to  decrease  the  lap  of  the  suction 
valve  at  the  head  end,  so  that  the  valve  opens  at  the  proper  time.  It  will 
close,  then,  a  trifle  after  the  crank  has  passed  the  dead  center,  in  this  case 
about  2  degrees  35  minutes  late  (see  Fig.  193).  The  reason  for  this  may 
be  seen  from  the  fact  that  the  inlet  valve  at  the  head  end  opens  after  the 
crank  has  passed  14  degrees  17  minutes  beyond  the  dead  center;  the  center 
of  the  eccentric  will  be 

81  degrees  34  minutes  -j-  14  degrees  17  minutes  =  95  degrees  51  minutes 

from  its  dead  center  at  the  head  end,  or  5  degrees  51  minutes  beyond  its 
mid  travel.  The  inlet  valve  remains  open  until  the  eccentric  reaches  the 
corresponding  position  on  its  return  stroke.  Opening  and  closing  must, 
therefore,  .take  place  while  the  eccentric  travels  through 

180  degrees  —  (2  X  5  degrees  51  minutes)  =  168  degrees  18  minutes. 

The  crank  moves  through  the  same  angle  and  the  piston  from  the  dead 
center  at  the  head  end  is 

14  degrees  17  minutes  +  168  degrees  18  minutes  =  182  degrees  35  minutes. 

The  piston  is,  therefore,  on  its  return  stroke  and  has  traveled  a  distance 
equal  to  the  radius  of  the  crank  times 

1  _  Cos.  2  degrees  35  minutes  =  R  (1  —  0.999)  =  0.018  in., 
an  insignificant  amount. 

Eeferring  to  the  valve  gear  itself,  the  working  edges  of  the  valves  and 
ports  are  shown  by  radial  lines  A,  B,  and  C,  Fig.  194,  on  the  ends  of  the 
valves  and  valve  chests,  at  the  side  of  the  cylinder  opposite  the  wrist  plate; 
for  each  port  there  is  a  mark  on  the  cylinder  coincident  with  the  edge  of  the 
port  which  is  toward  the  end  of  the  cylinder  barrel ;  and  for  each  valve 
a  mark  on  the  back  end  of  the  valve  coinciding  with  the  edge  of  the  valve 
which  is  toward  the  end  of  the  cylinder  barrel. 

Fig.  195  shows  the  wrist-plate  central  for  adjusting  the  valve  connec- 
tions. A  central  mark  on  the  back  hub  of  the  wrist  plate  and  three  marks 


192 


VALVE  SETTING 


AIR  COMPRESSORS 


193 


pug 


194 


VALVE   SETTING 


on  the  wrist-plate  stand,  which  is  bolted  to  the  cylinder,  show  how  the 
eccentric  motion  is  to  be  adjusted  so  that  the  wrist  plate  will  travel  cor- 
rectly when  in  motion.  The  two  outer  marks  indicate  the  extremes  of 
travel,  and  the  central  mark  of  the  wrist  plate,  when  in  line  with  the 
single  mark  on  the  hub,  shows  that  the  wrist  plate  is  central. 


To  SET  THE  SUCTION  VALVE 

To  set  the  suction  valve  as  shown  in  Fig.  195,  first  place  the  mark  on 
the  wrist-plate  hub  even  with  the  central  mark  on  the  wrist-plate  stand; 
then  adjust  the  valve  connections  to  give  the  suction  valves  the  lap  shown 


FIG.    194. 

on  the  drawing.  The  wrist  plate  should  now  be  connected  to  the  eccentric 
by  the  rods  and,  being  in  its  central  position,  the  rods  must  be  adjusted 
so  that  the  eccentric  also  is  in  its  center  of  motion.  The  eccentric  can  now 
be  secured  to  the  crank  shaft  after  the  crank  pin  is  moved  relatively  to 
the  center  of  eccentric  until  the  angle  included  between  their  respective 
centers  is  as  determined  by  the  calculation  given;  in  the  example,  81  de- 
grees 34  minutes,  the  eccentric  leading  the  crank  in  the  direction  of  motion. 
After  the  valves  have  been  set  as  accurately  as  possible  when  cold,  and 
the  movement  of  the  forward  and  back  strokes  equalized,  as  explained, 
indicator  diagrams  should  be  taken  and  the  eccentric  rod  adjusted  to  cor- 
rect any  slight  irregularities. 


AIR   COMPRESSORS 


195 


196 


VALVE   SETTING 


For  single-stage  air  compressors  and  in  the  high-pressure  cylinders  of 
two-stage  air  compressors  the  Allis-Chalincrs  Company,  of  Milwaukee,  uses 
as  a  standard  the  arrangement  of  valves  shown  in  Fig.  .I'.n;.  KVtary  valves 
are  used  for  the  inlet  and  plain  single-beat  poppet  valves  for  the  discharge. 
The  inlet  valves  are  driven  by  an  eccentric  on  the  main  shaft,  and,  by 
means  of  the  wrist  plate,  they  are  given  the  quick  opening  and  closing, 
and  the  slow  movement  when  the  ports  are  covered  and  the  valves  under 
pressure,  which  is  characteristic  of  the  Corliss  valve  gear.  The  inlet 
ports  are  of  ample  size,  short  and  direct,  and  the  air  is  guided  into  the 
cylinder  by  an  easy  curve,  thus  reducing  the  entering  friction  and  insur- 


FIG.  196. —  AIR  CYLINDER   WITH   AUTOMATIC   DISCHARGE. 

ing  the  complete  filling  of  the  cylinder  with  as  little  loss  in  pressure  and 
at  as  nearly  the  outside  pressure  as  possible. 

The  discharge  valves  are  of  the  drawn-steel  cup  type  and  open  auto- 
matically when  the  pressure  in  the  cylinder  equals  the  discharge  pressure. 

A  modification  of  the  valve  gear  shown  by  Fig.  196  is  illustrated  in 
Fig.  197.  In  this  gear  the  inlet  valves  are  operated  the  same  as  in  Fig. 
196,  but  the  discharge  valves  are  mechanically  closed,  being  free  to  open 
automatically,  and  positively  closed  by  plungers  operated  by  connections 
to  a  wrist  plate  driven  by  an  eccentric  on  the  main  shaft.  The  movement 
of  the  plungers  of  the  discharge  valves  is  so  timed  as  to  positively  bring 
the  valves  to  their  seats  just  as  the  piston  reaches  the  end  of  its  stroke, 
thus  avoiding  any  slip  of  air  back  by  the  valves  and  also  to  avoid  shimming 
when  the  piston  commences  to  return.  This  design  is  also  indicated  by 
Fig.  199,  showing  the  valve  gear  of  a  blowing  engine.  As  soon  as  the 
valves  are  closed  the  plungers  recede,  leaving  the  valves  held  to  their  seats 
by  the  discharge  air  pressure  until  that  point  in  the  return  stroke  of  the 


198 


VALVE  SETTING 


piston  is  reached  where  the  pressure  in  the  cylinder  equals  the  discharge 
pressure,  when  the  valves  are  free  to  open  automatically.  In  closing,  the 
air  between  the  plunger  and  valve  forms  a  cushion  which  is  so  adjusted 
and  gradually  reduced  that  the  valve  is  brought  gently  to  its  seat  without 
noise  or  pounding. 

A  third  type  of  valve  gear  is  shown  in  Fig.  198.  In  this  both  the  inlet 
and  discharge  valves  are  of  the  rotary  pattern,  positively  operated  by  inde- 
pendent eccentrics  on  the  main  shaft.  The  inlet  valves  are  the  same  as 
decribed  in  the  two  preceding  types.  The  discharge  valves  are  so  propor- 
tioned and  adjusted  as  to  close  positively  just  as  the  piston  reaches  the 


FIG.    198.  — AIR   CYLINDER  WITH   MECHANICAL   DISCHARGE   VALVE. 

end  of  its  stroke  and  to  open  at  any  predetermined  maximum  discharge 
pressure  required.  In  addition  to  the  rotary  discharge  valves,  the  cylinder 
is  fitted  with  auxiliary  poppet  valves  of  the  steel-cup  type,  which  serve 
as  relief  valves  in  case  the  eccentric  should  slip;  or  for  allowing  the  air 
to  be  discharged  from  the  cylinder,  should  the  pressure,  for  any  cause, 
fall  below  that  at  which  the  main  discharge  valves  are  set  to  open. 


How  TO  SET  BLOWING-ENGINE  VALVES 

Having  considered  the  procedure  necessary  for  setting  the  air  valves  of 
compressors,  together  with  some  of  the  factors  involved  in  their  design, 
it  will  be  of  interest,  in  conclusion,  to  note  the  directions  to  be  followed 
in  the  case  of  a  blowing  engine,  which,  although  very  simple,  is  sometimes 
puzzling  to  operating  engineers  lacking  exact  information  on  the  subject. 

Referring  to  Fig.  199,  when  the  engine  crank  pin  is  on  either  the  top 


AIR  COMPRESSORS 


199 


or  bottom  dead  center.,  set  the  wrist  plate  exactly  central;  that  is,  when 
the  piston  is  at  the  top  or  bottom  of  the  stroke,,  the  pins  M  M'  should  lie 
in  a  straight  line  between  P  C  and  P  C'. 

For  setting  the  inlet  valves  first  put  the  piston  at  the  top  of  its  stroke, 
the  wrist  plate  being  central,  adjust  the  connections  B  and  B'  until  the 


Horz.  Line £ 


Horz.  Line 


Horz..Line 


"Horz.  Lini 


FIG.    199. 


inlet  pins  D  D'  are  -     -  inches  from  the  horizontal  line,  and  adjust  the 

valve  stems  G  G  until  each  of  the  top  inlet  valves  are  lapped inches. 

Next  turn  the  engine  over,  set  the  piston  at  the  bottom  of  the  stroke,  the 
wrist  plate  again  being  central,  adjust  the  valve  stems  H  H  until  each  of 


AIR  COMPRESSORS  201 

the  bottom  inlet  valves  is  lapped  -  -  inches;  then  lock  the  valve  stems 
securely. 

For  setting  the  discharge  valves,  put  the  piston  at  the  bottom  of  the 
stroke,  the  wrist  plate  being  central,  adjust  the  connections  A  and  A'  until 
C  and  C"  are  each  -  -  inches  from  the  horizontal  line,  and  then  adjust 
the  valve  stems  E E  and  F F  until  each  of  the  valves  touches  its  seat; 
then  turn  off  a  quarter  turn  and  lock  them.  Then  turn  the  engine  over 
and  set  the  piston  at  top  of  the  stroke  and  see  that  the  valves  are  in  the 
same  position  as  when  the  piston  was  at  the  bottom. 

The  amount  of  lap,  etc.,  indicated  by  the  spaces  in  these  directions 
varies,  of  course,  with  each  machine,  and  the  figures  can  either  be  obtained 
from  the  builders,  or  may  be  worked  out  in  accordance  with  the  method 
described  earlier  in  this  chapter. 

In  the  various  gears  described  the  valves  are  placed  in  the  cylinder 
heads,  thus  reducing  the  clearance  to  the  minimum ;  all  of  these  valves  are 
readily  accessible  and  can  be  removed  and  replaced  without  difficulty  and 
without  disturbing  the  adjustment.  It  may  be  said,  also,  that  while  the 
foregoing  mentions  only  compressors  and  blowers  for  handling  air,  it  applies 
as  well  to  machines  designed  for  other  gases,  as  far  as  the  general  principles 
involved  are  concerned.  Special  apparatus,  however,  requires  special  treat- 
ment and  the  builders  should  in  all  cases  be  required  to  furnish  specific 
directions  for  setting  the  valve  gear  supplied  with  their  machines.  With- 
out this,  misunderstandings  occur  which  sometimes  cause  serious  trouble. 


INDEX 


Admission,  angle 12 

effect  of  angularity  of  con- 
necting rod 15 

of    changing    valve 

setting 20 

of  steam 39,  40 

openings,  maximum 101 

period 13 

point  of. . .  .33,  34,  35,  36,  124 

finding 21 

Advance,  angle 34,  36,  116 

angle,  finding.  .21,  22,  23,  24,  26 

maximum 45 

angular,  effect  of  changing. . 

127,  128 

of  eccentric,  angular,  chang- 
ing      19 

Ahead  of  crank,  defined 43 

Aikens,  Claude 188 

Air  compressors 188 

compressor,  volumetric  efficiency .   1 88 
with   automatic   dis- 
charge    196 

cylinder    with    mechanical    dis- 
charge valve 197,  198 

Allis-Chalmers  Co 172,  196 

Angle  behind  crank,  cut-off  valve. . .  44,  45 
crank,  corresponding  to  piston 

movement 190 

of  admission 12 

of  advance 34,  36,  116 

finding. 21,  22,  23,  24,  26 

maximum 45 

of  rod,  correcting  for 18 

finding 16 

Angular  advance,  effect  of  changing. . 

127,  128 

finding 12 

of  eccentric..  11,  84,  99 
of  eccentric,  chang- 
ing  19,  20 


PAGE 

Angularity  of  connecting  rod 15,  191 

of  rod,  correcting  for 17 

Balanced  piston  valve 135 

steam  valve 115 

valves 93,  96,  103,  108,  113 

Behind  crank,  defined 44 

Blowing-engine  valves,  setting 198 

Brown  engine 76 

governor 78 

setting  valves 79 

Buckeye  engine 92 

piston  valve 100 

Cam,  trip 68 

Catch  block,  clearance 59 

Center,  dead 35,  39,  51 

finding 46,  122 

line 49,  50 

putting  engine  on 138 

Central  marks  on  hub  of  wrist  plate. .     59 
Centralization  of  valve  gear,  double 

eccentric  engine 61 

Circle,  crank 36 

of  reference 36 

valve 30 

Clearance,  amount 88 

at  catch  block 59 

at  ends  of  steam  cylinder, 

equalizing 53,  54 

obtaining 80 

of  cylinder 53,  54 

on  valve  rod 180 

space 188 

Compound  engine 125 

Sturtevant 135 

Compression 126 

amount 82,  148 

effect  of  changing  valve 

setting 20 

point  of 34,  35,  36 


203 


204 


INDEX 


Compression,  point  of,  finding 23 

Condensing  engine,  lead  of  low-pres- 
sure valve 125 

Connecting  rod,  angle,  finding 16 

angularity 15,  191 

Conliss  engines,  tables  showing  prin- 
cipal dimensions  and  horse 
power  with  different  steam 
pressures  and  points  of  cut- 
off  56,  57 

steam  engines 53 

Correcting  for  angle  of  rod 17,  18 

Crank  angle  corresponding  to  piston 

movement 190 

when    compression    be- 
gins, finding 27 

circle 36 

on  dead  center 47 

pin  and  eccentric,  determining 

relative  positions 190 

position 115 

position. 6,  7,  8,  9,  30,  32,  33,  39,  40 

travel 41 

Cross-compound   engine,    setting  ec- 
centric     127 

Cross-exhaust  closed 186 

open 187 

valve 181 

Cut-off 40,  168,  174 

adjusting 127 

changing 82 

early 43,45,46,  127,  167 

Greene 62 

late 45,  127,  167 

later  than  one-half  stroke 45 

point  of .  .4,  15,  18,  34,  35,  36, 

40,  41,  42,  43,  44,  99,  124 

point  of,  finding 23,  24 

Reynolds  long-range 172 

rods,   adjusting,   Rice  &  Sar- 
gent engine 150 

valve 95,  97 

Meyer 38,  39 

operation 38 

position 99 

Cylinder  pressure ...     96 

valves,  details 107 

D  slide  valve 19 

Dashpot  rod,  length 58,  59,  154 

stem,  adjusting 80 


PAGE 

Dead  center 35,  39,  51 

finding 46,  122 

Details    and    measurements,    Sturte- 

vant  compound  engines.. .  .    144 

of  link 107 

Diagram,  indicator 35,  119 

making 9 

necessary    data    for    con- 
structing      36 

of  high-speed  engine 35 

of  side  shaft 131 

taking 142 

using 19 

valve,  use 21,  30 

Zeuner  slide-valve 23,  29 

Dimensions  with  different  steam  pres- 
sures and  points  of  cut-off,  Corliss 

engines 56,  57 

Double  eccentric  engine,  valve  setting, 

60,  61 

Double-ported  main  valve 97 

valves 1 56 

Dow,  Carl  S 135 

Drainage  systems 142 

Duplex  pump 180 

Eccentric 40 

adjustable 135 

low-pressure 139 

and  crank  pin,  determining 

relative  positions 190 

angular  advance 1 1,  84,  99 

changing  .19,  20 
cross-compound  engine,  set- 
ting    127 

linear  advance 11 

low-pressure,  adjusting 137 

motion,  adjusting 194 

on  dead  center 47,  48 

point  of  minimum  cut-off.. .   126 
position  ..3,6,  7,  8,  9,  32,  39, 
40,  41,  45,  46,  51, 

115,  176 

changing 43 

rod,  length  .  .42,  73,  75,  170,  171 

too  long 72 

setting 101,  102 

travel 41,  46,  70,  165 

Eccentricity,  changing 20 

Engine,  Brown 76 

Buckeye 92 


INDEX 


205 


Engine,  changing  speed 150 

compound 125 

Fitchburg Ill 

Fleming  piston-valve 121 

Greene-Wheelock 62 

heavy  duty 156 

Mclntosh  &  Seymour 84 

Porter-Allen 103 

Putnam 130 

putting  on  center 138 

"Reliance" 156 

Rice  &  Sargent 145 

setting  at  half  stroke 51 

steam,  Corliss 53 

Sturtevant  compound 135 

Wright 159 

Equality     of     maximum     admission 

openings 101 

Equalizing  pressure  in  exhaust  pipes. .    181 

Exhaust 15 

clearance 11 

effect  of  changing  valve  set- 
ting       20 

gear 147 

lap 32,36 

definition 10 

effect  of  changing 128 

positive  and  negative 10 

lead 33,34,36 

motion 115 

point  of 17 

valve 68,  113 

valves,  adjusting 75 

equalizing  movement     81 

rod,  length 60 

setting 81,  148 

stem,  length 81 

Expansion,  effect  of  changing  valve 
setting 20 

Fitchburg  engine Ill 

Flat-balanced  valves 108 

Flat-side  valves 103 

Flat  valve 93,  96,  108 

Fleming  piston-valve  engines 121 

Gauge  for  adjusting  clearance 54 

Gear,  details 86 

valve 103,  111 

Governor,  adjusting 82,  143 

Brown  engine 78 


Governor,  case,  location 117 

in  position , .  .  , .    139 

inertia 1SS,  139 

Porter  fly-ball 106 

position 99 

Rites  inertia,  Rice  &  Sar- 
gent engines 149 

rod,  adjusting 60 

shaft 119 

Greene  cut-off 62 

Greene-Wheelock  engine 62 

setting 

valves..     73 

valve  gear.     64 

Gridiron  valve 62,  84,  88,  159,  161 

Hall,  Thomas , 121 

Hawkins,  E.  S 19,  29 

Heavy  duty  engines 156 

High-pressure  side  of  Greene-Wheel- 
ock cross-compound 

engine 63 

valve 140 

setting 138 

Hill  valve 62 

Horizontal  engine,  valve  gear 84 

travel  of  pin 97 

Horse  power  with  different  steam 
pressures  and  points  of  cut-off,  Cor- 
liss engines 56,  57 

Indicator  diagram 35,  194 

making 9 

rig 141 

use 30,  82,  118,  134,  142 

Inertia  governor 138,  139 

Inlet  valve 65,  67 

gear,  operation 146 

Inside  lap 32 

Johnson,  F.  L '. 130 

Keying  up  pin  bearings 120 

Lap 32,  50,  163,  165,  175 

adjusting 79,  89,  157 

valves  for 75 

amount 59,  154,  177,  194,  201 

changing 19,  20 

definition 4 

effect. .  ...       4 


206 


INDEX 


Lap,  exhaust 10,  32,  36 

definition 10 

effect  of  changing 127,  128 

finding 21,  23,  24,  25,  26,  27 

inside 32 

necessity  for 31 

negative,  definition 11 

outside 32 

steam 31,  32 

effect  of  changing 127,  128 

use 4 

valve 45,  46 

Laying  out  valve  motion 18 

Lead 33,  51 

action 4 

amount 

81,  82,  89,  99,  122,  126,  137,  177 

definition 4 

effect 3 

exhaust 33,  34,  36 

finding 21,  23,  27 

for  setting  valves 155 

of  low-pressure  valve,  condensing 

engine 125 

of  low-pressure  valve,  non-con- 
densing engine 125 

on    bottom    end,    low-pressure 

valve  side 139 

steam 34 

valve  showing 98 

Linear  advance  of  eccentric 11 

Link,  details 107 

in  valve  gear 103,  104 

Low-pressure  eccentric,  adjustable. . .   139 

adjusting 137 

valve 135 

back  platen 137 

setting 126,  135 

side  showing  lead 

on  bottom  end.   139 
side  showing  lead 
on  top  end 137 

Mclntosh  &  Seymour  engine 84 

Main  valve,  action 46,  48 

in  position. ; 49 

of  Meyer  combination  .  38,  39 
setting 101 

Marks  on  valve  seat 59 

stems 101 

Maximum  admission  openings 101 


Maximum  opening 36 

port  opening 124 

travel  of  valve 167 

Meyer  cut-off  valve 38 

Minimum  travel  of  valve 168 

Multiported  cut-off  valve 45 

valve 46,  76,  84,  97 

Negative  exhaust  lap 10 

lap,  definition 11 

Nickel,  F.  F 180 

Non-condensing  engine,  lead  of  low- 
pressure  valve 125 

Opening,  maximum 36 

Outlet  valve 65,  68 

Outside  lap 31,  32 

Period  of  admission 13 

finding 14 

Piston,  position 6,  7,  8,  9 

finding 26 

valve 96 

Buckeye 100 

engine 121 

engines,    table    showing 
effect     steam     lap,     ex- 
haust lap,  travel  and 

angular  advance 128 

Platen  of  low-pressure  valve 135,  137 

Plates,  pressure 107,  108 

Plock,  John  L 53 

Plug,  valve 64,  65 

Plumbing  wrist  plate  and  rocker  arm .     58 
Point  of  admission.  .21,  33,  34,  35,  36,  124 

of  compression 34,  35,  36 

finding 23 

of  cut-off.  .4,  15,  18,  34,  35,  36, 

40,  41,  42,  43,  44,  99,  124 
Corliss  engines. . .  .;">('>,  :>7 

finding 22,  24 

of  exhaust 17 

release 18,  34,  35,  36,  40,  71 

finding •_>:; 

Port  opening,  maximum 124 

steam,  width 34 

width 37 

Porter- Allen  engine 103 

Porter  fiy-ball  governor 106 

Position  of  eccentric  ..  .41,  45,  46,  51,  176 
changing 43 


INDEX 


207 


Position  of  valves 41 

Positive  exhaust  lap 10 

Pressure,  cylinder 96 

equalizing  in  exhaust  pipes.  181 

plates,  details 107,  108 

zero  point 185 

Pump,  duplex 180 

Putnam  engine 130 

valve  gear 129 

Radius,  eccentric,  changing 20 

Reach  rod,  length 58 

Regulator,  Putnam  engine 130,  132 

Release,  point  of. .  18,  23,  34,  35,  36,  40,  71 

"Reliance"  engines 156 

Reynolds  (1890)    and    girder    frame 

Corliss  engines 152 

long-range  cut-off 172 

Rice  &  Sargent  engine 145 

Riding  cut-off  valve. 38 

Rites  inertia  governor 135,  143 

Rice  &  Sargent 

engines 149 

Rock  shaft 134 

Rocker  arm . 94,  171 

plumbing 58 

Rod,  angle,  finding 16 

correcting  for  angle  of 17,  18 

cut-off,  adjusting 150 

dashpot,  length 58,  59,  154 

eccentric,  length.  .42,  73,  75, 170, 171 

too  long 72 

exhaust  valve,  length 60 

governor,  adjusting 60 

length 46 

reach,  length 58 

test  for  proper  length 101 

valve,  length 168 

Safety  stop,  setting 82 

Seats,  valve 88 

Separate  steam  and  exhaust  valves ...  113 

Setting  blowing-engine  valves 198 

eccentric 102 

engine  at  half  stroke 51 

exhaust  valve 81 

high-pressure  valve 138 

main  valve  and  eccentric.  ...  101 

piston  valves 100 

safety  stop 82 


Setting  steam  valves 74,  108 

suction  valve 194 

valves 29,  46 

Brown  engine 79 

Buckeye  engine 97 

Fitchburg  engine. ..  1 1 7,  119 
Fleming    piston  -  valve 

engine 121 

Greene-Wheelock      en- 
gine       73 

^horizontal  Corliss  steam 

engines 54 

Mclntosh    &    Seymour 

engine 89 

Porter- Allen  engine. ...    109 

Putnam  engine 130 

Reynolds     long  -  range 

cut-off 177 

Rice  &  Sargent  engine. .    147 

Wright  engine 168 

Shaft  governor,  action 119 

Side  shaft,  diagram 131 

Slide  valve 3 

D 19 

Speed  of  valve  motion 41,  42 

Steam,  admission 40 

and   cut-off,    Meyer 

cut-off  valve 39 

chest,  valves  removed 49 

engines,  Corliss 53 

lap 4,  31,  32 

effect  of  changing 127,  128 

use 4 

lead 34 

port,  width 34 

pressures,  Corliss  engines  . .  .  56,  57 

valve 113,  114 

balanced 115 

equalizing  movement. . .     82 

motion 115 

open  at  both  ends  when 

hooked  up 174 

operation 76 

setting 74,  108 

Steam,  exhaust  valve,  length 81 

valve,  length 1 70 

marks 101 

Stroke,  adjusting 89 

events,  determining 124 

measuring 91 

Sturtevant  compound  engine 135 


208 


INDEX 


Sturtevant  compound  engines,  details 
and  meas- 
urements. .  .  144 

Suction  air  valve,  opening 188 

valve,  setting 194 

Table  of  laps   and   lead  for   setting 

valves 155 

showing  effect  of  changing 
steam  lap,  exhaust  lap, 
travel  and  angular  advance, 

for  piston- valve  engines 128 

Tandem  compounds,  valve  setting. . .   125 

Templets  for  valve  setting 122 

Test  for  proper  length  of  rods 101 

Tipping  motion  of  link 104 

Travel 101 

direction 41 

elfect  of  changing 127,  128 

horizontal,  of  pin 97 

of  crank 41 

of  eccentric 70 

of  valve.  .32,  34,  36,  39,  41,  42, 
46,  70,  74,  84,  95,  97, 
114,  117,  165,  167, 

168,  170 

adjusting 73 

changing 20 

finding 22,  23,  26,  27 

Trip  cam 68 

Trouble,  causes 72 

Trunnions,  position 110 

Valve  action 6,  175 

Meyer  combination 39 

adjusting Ill,  117 

for  lap 75 

and  steam  passages,  sectional 

view,  Putnam  engine 132 

arrangement  in  cylinder 161 

balanced.  .93,  96,  103,  113,  115, 135 

chest 93,  94 

circle 30 

cross-exhaust 181 

cut-off 95,  97 

position 99 

cylinder,  details 107 

D  slide 19 

diagram,  use 21,  30 

double-ported 97,  156 

equalizing  movement 81 


Valve  exhaust 68,  113 

adjusting 75 

setting 81,  148 

flat 93,96,  103 

gear 103,  196,  198 

air  compressor 191 

Buckeye  engine 92,  93 

centralization,    double   ec- 
centric engine 61 

Fitchburg  engine Ill,  112 

Greene-Wheelock  engine  . .     64 

operation 146 

Putnam  engine 129 

gridiron 62,  84,  88,  159,  161 

high-pressure 138,  140 

Hill 62 

inlet 65,  67 

lap 45,  46 

low-pressure 135 

main,  action 46 

adjusting  action 48 

in  position 49 

Meyer  cut-off 38 

motion 111,  113 

laying  out 18 

speed 41,42 

movement 87,  159,  164 

multiported 76,  84,  97 

operation 85 

outlet 65,  68 

piston 96,  100 

plug 64,  65 

position 41 

corresponding  to  given 

crank  position 30 

riding  cut-off 38 

rods,  length 168 

seats 88 

seat,  marks 59 

setting 29,  46 

Brown  engine 79 

Buckeye  engine 97 

double  eccentric  engine . 

60,61 

effects  of  changing 19 

Fitchburg  engine.  .  .117,  119 
Fleming      piston  -  valve 

engine 121 

Greene-Wheelock  engine     73 
horizontal  Corliss  steam 
engines 54 


INDEX 


209 


Valve  setting,  Mclntosh  &  Seymour 

engine 89 

Porter- Allen  engine 108 

Putnam  engine 130 

Reynolds      long  -  range 

cut-off 177 

Rice  &  Sargent  engine .  .    147 

Wright  engine 168 

showing  lead 98 

slide 3 

steam 113,  114 

equalizing  movement. ...     82 
open  at  both  ends  when 

hooked  up 174 

operation 76 

setting 74 

stems,  length 1 70 

marks 101 

suction,  opening 188 

travel.  .4,  10,  11,  32,  34,  36,  39, 
42,  70,  73,  74,  84,  95, 
97,  114,  117,  165,  167, 

168,  170,  185,  188 
changing 20 


Valve  travel,  finding 22,  23,  26,  27 

with  and  without  lap. ...       4 

Volume,  zero  point 185 

Volumetric  efficiency  of  compressor. .   188 

Wedge  adjustment  for  keying  up  pin 

bearings 120 

Wheelock  arrangement  of  valves  ....     62 
Wright  automatic  cut-off  engine,  view 

of  exhaust  side 160 

automatic  cut-off  engine,  view 

of  steam  side 158 

steam  engine 159 

William 159 

Wrist  plate..  154,  157,  161,  162,  164, 

168,  178,  191,  199,  201 

centering 170 

central  marks  on  hub  ....     59 

in  extreme  position 59 

plumbing 58 

Zero  point  of  pressure  and  volume. .  .    185 
Zeuner  slide-valve  diagram 23,  29 


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